The Brink of Death was the fourth and final story in the audio anthology The Sixth Doctor: The Last Adventure, produced by Big Finish Productions. It was written by Nicholas Briggs and featured Colin Baker as the Sixth Doctor and Bonnie Langford as Melanie Bush.
It serves as the final chronological story for the Sixth Doctor played by Colin Baker, filling in a critical missing piece of the Doctor's existence and leading directly into the 1987 television story Time and the Rani.
It is prominent for depicting the events leading up to the Sixth Doctor's regeneration into the Seventh Doctor for the first time in performed media with the original actors, and the second official account, following 2005's Spiral Scratch.
The story also provides an explanation for the Seventh Doctor's development into a Machiavellian plotter after regenerating, as well as why the Doctor seems to grow darker and more morally unclear with each passing incarnation, by showing here that he deliberately chose to let go of his reliance on some form of moral crutch if it meant the difference between taking down an enemy before they could inflict great harm on existence or faltering at the moment of truth and suffering the consequences. He would then shift back toward pragmatic ways of dealing with problems as they arose, similar to his first incarnation, and continue this descent many times over.
Mel, riding a battery-powered vehicle comparable to a skimmer, is attempting to escape a group of flying lizards. Trying to contact the Doctor through the vehicle's communication device, Mel is only able to get a couple of garbled messages from him. The lizards are able to get a hit on the vehicle's engines, causing its battery to start dying, which enables them to catch even more up to Mel. The Doctor, unable to teleport Mel back to the TARDIS, instead teleports himself into the cockpit of the vehicle and then sets off the ejector seats, which he uses as retrorockets to land him and Mel safely next to the parked TARDIS. Mel asks him if that was also part of the plan, but the Doctor admits that it was more luck than anything else. The two then promptly leave the dangerous world.
Mel says that that planet didn't live up to the picture the Doctor had painted of it, as a place with computer science and sea-side resorts. The Doctor reminds her that at least it was better than the deadly radiation they were able to avoid in the Lakertyan System. Mel points out that the Doctor still brought them to the wrong planet: They were going to Zastros 8 but ended up on Zastros 9, to which the Doctor replies that the TARDIS has been acting much more strange than usually of lately. As if on cue, sparks and smoke start coming up from under the console, and the Doctor tells Mel he will go below and take a look at it. Just after the Doctor has disappeared from view, a strangle sound comes from beneath the console, and Mel asks the Doctor if he is alright. But instead of the Doctor it is the Valeyard who comes back up, and he assures Mel that he is "just fine". Mel stares stunned at him, prompting him to ask if anything is wrong with her. Mel, slightly confused, says that she felt like she was having a headache for a moment, but she is alright now. Mel then addresses the Valeyard as "Doctor" and asks him where they are going now as if he had always been there. "Where indeed," asks the Valeyard, "when all of space and time is our oyster?" He then laughs in triumph.
Meanwhile, the Doctor finds himself somewhere dark, empty, and cold. He calls out, first for Mel then anyone at all, but finds out that, wherever he is, he is utterly alone.
Elsewhere, a TARDIS lands on a rundown space station, and a Time Lady steps out, humming to herself. Shortly after arriving, she gets a call from her boss, Storin, who addresses her as Demolition Coordinator Genesta and asks for her report. Annoyed, Genesta surly replies that she has only just arrived, but Storin presses the issue and she replies that from where she is standing, it doesn't look good at all. Storin then goes on to explain that the demolition of the station is a priority to the new administration, and Genesta replies that she is well aware of that. Noticing her annoyance, Storin reminds her that her service records already contains several formal reprimands regarding her attitude and he advises her to get on with the job. Genesta hangs up as she calls him a "pillock", and continues onward, making notes about the state of the space station, which turns out to belong to the Celestial Intervention Agency, and she notices that it is in an advanced state of disrepair as it has been abandoned for some time and the higher-ups was trying to hide its existence. Suddenly, Genesta hears a voice calling out for help and goes on to investigate.
The Doctor is still calling out, asking if anyone at all can hear him, while trying to figure out what has happened to him. Suddenly, he hears someone calling back. It turns out it is Genesta. The Doctor states his identity and asks her where he is. Genesta tells him that he was lucky she heard him as his voice came from behind an old panel. She then finds out that the panel is actually a concealed conduit to the Matrix, which turns out to be where the Doctor has ended up. Genesta tells him he appears to be an after-image and warns him that he is about to be deleted by a diagnostics check. The Doctor asks her how she knows that, and she answers that she studies Matrix Diagnostics in night school. He then asks her to explain why he appears to be an after-image, and replies that it is probably because he is dead.
Meanwhile, the Valeyard has repaired the TARDIS, and is preparing to land. Mel, still addressing him as "Doctor", asks if they are going to Zastros 8, but he replies that there has been a change of plans and cryptically states that he has "a little errand to run" and they are landing on the planet Plestinious.
The Doctor desperately tries to convince Genesta that he is not dead, telling her he was standing in his TARDIS a mere few moments ago. Genesta suggest that he could also be a glitch in the Matrix, and that either way he is going to be erased by the diagnostic tools soon. The Doctor asks if she can stop them, and she replies she can but she is not sure if she should. The Doctor tries appealing to her sense for mystery, pointing out she is going to night school, so she must obviously want more challenges in life, and tells her that he is such a challenge; a puzzle to solve. Genesta falls silent for a moment, and decides to help him, starting with looking him up in the database. But after checking, she says he cannot be the Doctor, as he is currently in his TARDIS with an Earthling, and the Matrix is still receiving the usual updates from the TARDIS' symbiotic nuclei. The Doctor begs her to keep investigating and stop the diagnostics, before asking her how long he has left, to which she replies "six minutes." The Doctor then tries to appeal her sense of sympathy, stating that she is all that stands between him and oblivion.
Suddenly, the Doctor is pulled out of the Matrix and manifests physically in the space station and stands face to face with Genesta, who informs him that she has managed to temporarily stop the erasure with four minutes left to go. Genesta tells him that he certainly looks nothing like the guy the database told her was the sixth incarnation of the Doctor. The Doctor asks if he can have a look, and immediately recognises the person on the screen as the Valeyard.
The Valeyard and Mel have landed on Plestinious, and are walking through one of its cities, which Mel thinks looks like something out of "the late 60's or early 70's". She tries asking the Valeyard about his mysterious errand, but he remains cryptic and tells her that he will handle it alone, telling her she can pass the time by taking a look around the city.
On the space station, Genesta welcomes the Doctor back to the land of the living, though she is still in doubt about whether or not he is the real one. The Doctor points out that the fact that he can walk around outside the Matrix at least proves that he is neither a glitch nor an after-image. He commends Genesta for helping him, pointing out that she is taking quite the chance by doing so, to which Genesta replies that she actually enjoys taking this risk. The Doctor then comments that Genesta has a very noticeable accent, and she tells him that when she was young she went on a field trip to Earth — more precisely Yorkshire in England — and loved being there, so much so that she stayed behind for several years before the CIA was able to find her and drag her back to Gallifrey. The Doctor, impressed by this, tells her that in some ways she reminds him of himself, but he will tell her that story later. The Doctor suggests that they use Genesta's TARDIS to catch up to the Valeyard, seeing how her looking him up through the Matrix should mean she will have received his coordinates. Genesta speculates that this would probably make Storin very angry, so she gleefully agrees to it.
Meanwhile, Mel sees the Valeyard off, as he heads out by boat. Soon after this, she is approached by a strange woman, who tells her that the boat sails to a nearby volcano. Mel asks if the volcano is active, to which the woman replies that it grumbles now and then as the nature's way of showing disapproval over what the local authorities did to Plestinious's moon. Since Mel is puzzled by this, the woman explains that though the moon didn't use to glow both night and day; it does so now because it was turned into a power plant, a process which killed the moon's local life. The woman, clearly angry, explains that though the life on the moon weren't plants or animals and was dismissed by the local authorities as being just bacteria, it was more than that; people like the woman, the ones "see more", know this to be true as they felt the creatures dying. The woman then starts to inquiring about "the Doctor", asking Mel if she has known him long. A little unsure, Mel answers that she thinks so. The woman picks up on this and tells Mel that she can sense she is in doubt, like something is wrong. Finding the whole conversation strange, Mel asks the woman who is, and she replies that her name is Lorelas, and she offers Mel one of the luck charms and seeing stones she is carrying around, telling her they could help her see things more clearly. Mel, now believing Lorelas to be a phony fortune-teller trying to load off her useless trinkets, tells her that she will have to improve her spiel if she wants to sell her something, but Lorelas tells that just maybe she isn't interested in selling anything and want help her with finding who "the Doctor" really is, and will tell her one thing for free: "You're lying to yourself, my friend. And you know it." Mel begins walking away, but Lorelas calls her by name, telling her that she knows it to be true.
Walking without looking, Mel bumps into Genesta. Mel fears for moment that Genesta is also trying to sell her something, but she ensures her that she isn't. She just wants her to look at a strange-looking man who is following her and tell her if she knows who he is. The strange-looking man is actually the Doctor, but despite getting a clear look from a distance, Mel doesn't recognise him. Genesta returns to the Doctor and tells him this, and he starts worrying about what the Valeyard might have done to Mel. Genesta also tells him that she learned that the Valeyard took a boat to the nearby volcano. The Doctor declares that they'd better be on the next boat.
From a distance, the Doctor and Genesta observe the Valeyard through a pair of binoculars, as he reaches the top of the volcano. He releases a strange flying metal device into the volcano which then returns to him shortly after. As he starts walking back down, the Doctor decides that they must better do the same before he sees them. The Doctor and Genesta then manage to find the TARDIS and Mel just as the Valeyard returns. Mel asks the Valeyard if his errand was successful, and he replies it was. The Doctor, declaring he will not stand for it any more, decides to confront the Valeyard despite Genesta's protests. The Valeyard at first pretends that he doesn't recognise the Doctor, so he tries talking to Mel instead, but she does not appear to hear nor see him. The Valeyard spitefully tells the Doctor that he will only exist for six more minutes before bidding him goodbye and closing the TARDIS door. As the Doctor starts banging on the door, demanding to be let in, Genesta tells him to calm down before he attracts undue attention, but the Doctor replies he can't; the Valeyard knows about his predicament and the fact that he is living on borrowed time. Genesta suggests that maybe they should attempt to see if they can learn more about who and what the Valeyard is, as it might help her believe that the Doctor is telling the truth. The Doctor, outraged, tells her that what she has seen so far should clear prove that the Valeyard is up to something, but mid-sentence he is suddenly pulled back into the Matrix as a shocked Genesta calls out for him by name.
Inside the TARDIS, Mel says she thinks she heard shouting and banging on the door, but the Valeyard dismisses it as noise from the marketplace. Mel then asks him what he is doing with the metal container in his hands, and the Valeyard claims he is just "topping the old girl off a bit." Mel asks if he means with fuel, and he answers that it is sort of like that.
Genesta once again finds the Doctor inside the Matrix, and he thanks her for calling him Doctor. Genesta tells him that she has more bad news. Despite her best efforts to get back with her TARDIS as quickly as possible and stop his erasure, something was trying to hold her back, so she was only able to freeze it with three minutes left to go. She explains that, though she knew it would get her into trouble, she was also able to do some digging in the Time Lord Forbidden Files. According to the files she found, the Valeyard was apparently created as a construct by a Time Lord Black Ops division as some sort of weapon. Realising that the situation is getting serious, the Doctor suggests that the two of them contact Storin in the hopes that he could arrange for a meeting with the High Council so the whole affair can be sorted out.
Storin, however, is not terribly helpful and quite sceptical of the Doctor's claims, pointing out that Genesta after all discovered him in a decommissioned Matrix port. The Doctor insists that their evidence clearly shows that the Valeyard has altered Matrix records and taken the Doctor's place. Storin considers this and replies that the Doctor's allegations are quite serious if true and asks the Doctor what he should do about them. The Doctor demands that he brings them to the attention of the Council so he can get an audience with them. Storin replies by laughing heartedly, and suddenly his form dissolves in front of the Doctor and Genesta's eyes and transforms into that of the Valeyard. Shocked, the Doctor asks the Valeyard how he is capable of doing this, and the Valeyard gloatingly replies that there soon will no limits to what he can do, before the Doctor is once again pulled into the Matrix.
Inside the Matrix, the Doctor wonders about what the Valeyard just said, before Genesta again manages to contact him and get him out. She warns him that they have lost yet another minute, and it was even more difficult stopping it this time, like some strange power was controlling the Matrix. She also points out that it is worrying that the Valeyard has managed to replace both the Doctor and Storin, so they should hurry up in finding out what is happening. She explains that she has managed to trace the strange power to the Doctor's TARDIS, something which the Doctor at this state doesn't find surprising at all, and he says they need to use Genesta's TARDIS once again.
In Genesta's TARDIS, Genesta explains that she was already tracking the power from the Doctor's TARDIS, so they quickly lock on to it. The Doctor concludes that the Valeyard probably has replaced Storin in the same way he replaced him, wondering if that could mean that poor Storin is at this very moment being erased as a glitch in the Matrix, and he worries that the Valeyard might have the power to replace even more Time Lords with himself. The Doctor manages to find the point in time where the strange power started emanating from his TARDIS and arrange to arrive a few minutes earlier than that. Looking at his TARDIS from the scanner, the Doctor discovers that it is parked in the square of the werewolf town, realising that it was the Valeyard who had place the key in the TARDIS back then. He decides that he must get into his TARDIS, confront the Valeyard, and stop him before he manages to accomplish whatever it is he is going to do.
Entering his TARDIS, the Doctor finds the Valeyard fiddling with the controls. The Doctor demands that stops, but the Valeyard answers that he is too late; he just finished with the task he needed to do. The Valeyard then calls the Doctor out on breaking the laws of time by crossing his own timeline like this to interfere with the past, telling him he is far more like him than he'd care to admit. The Doctor answers that he is nothing like him and he has only done what he did in order to stop him. "So you'll do anything to stop me, is that it?" says the Valeyard smugly, "That sounds like an argument in favour of total war. How does that sit with your precious moral scruples?" Indignant, the Doctor demands that the Valeyard explains himself, which he agrees to, telling the Doctor that he will probably find his plan quite ingenious. The Valeyard explains that he has inserted something into the symbiotic nuclei of the Doctor's TARDIS; a cluster of microscopic telepathic creatures that can only survive in volcanic gasses. The Doctor realises that it explains what the Valeyard was doing on the volcano, something which happens in the Valeyard's personal future. The Valeyard reveals the name of the creatures as "the Nathemus", explaining that they come from Plestinious's moon, where he saved them from going extinct when the local authorities destroyed their natural habitat by converting the satellite into a power plant. By rescuing the creatures, the Valeyard ensured that they become eternally loyal to him, and so he promised them a fascinating and colourful mind to feed off; the Doctor's. He explains that over time, the Nathemus will build up their strength as they feed, so they can finally repay their debt of gratitude to him.
In response, the Doctor declares he will try to personally contact the Nathemus and convince them to back down from the plan. But the Valeyard just laughs in amusement at this. Suddenly, and much to his confusion, the Doctor finds himself instantly transported to a strange place and somehow Genesta is there too. The Doctor barley has time to expresses his puzzlement over how they both ended up in this place, before they realise that the strange place is growing smaller around them and threatens to crush them both. Genesta spots an escape in the form of a tunnel, and her and the Doctor make a run for it. The Doctor soon notices that they are surrounded by other beings, who are running towards the same exit as them, but he can't make out what they are. The creatures explain that they are the Nathemus and that someone is saving them. The Doctor then discovers that the tunnel is looking like a metal tube, and realises that he is seeing a vision, showing how the Valeyard saved the Nathemus in the first place. The vision dissolves and the Doctor finds himself and Genesta surrounded by the Nathemus. Once again he wonders why she is there, since it was just him who contacted the Nathemus. He then speaks to some of the creatures, trying to explain to them that the Valeyard has tricked and used them, but they rebuff him, telling him that the Valeyard has saved them and given them both food and volcanic gas to live in. They explain that in exchange they think about the Valeyard and thereby plant the thoughts of him in many minds. The Doctor realises that the "many minds" is actually the Matrix and they are using the connection through his TARDIS' symbiotic nuclei to influence it, enabling the Valeyard to take it completely over.
The vision then ends, and the Doctor is back in the TARDIS, once again standing face to face with the Valeyard. The Doctor, utterly horrified by what he just has learned, asks him if his plan is to replace every Time Lord with himself. The Valeyard gloats that his plan goes beyond even that; he will take over every Time Lord that has ever lived, so that one day he will even become Rassilon himself and be able to shape Time Lord society in his own image. The Doctor asks him why Genesta was in his telepathic vision, since she just a mere technician, but the Valeyard claims to not know anything about her since the Doctor is from his future, he has only just started his plan and needs to be at height of his power before he can take advantage of it. The Doctor realises that this is also the time he stole the psychic extractor from the Red House, so he could use it to steal energy from the Doctor at the New Regency Theatre. The Valeyard is happy to hear his scheme will work, but the Doctor states that he is still determined to stop him. The Valeyard gloatingly tells him that he is actually rather powerless to do anything about it and laughs in triumph as he sees that that the Doctor is being dragged back into the Matrix.
The Doctor realises that the Matrix is becoming ever colder as Genesta finds him once again. She tells him that he only has one minute left now and the power from the Nathemus is overwhelming the Matrix as they speak, so she wasn't able to freeze the erasure this time and could only slow it down, so she doesn't know exactly how much time the Doctor has left. The Doctor then collapses from exhaustion, and Genesta grabs him, telling him he should try to relax, to which the Doctor answers that he can't as long as the Valeyard is out there. She ask him if the Valeyard isn't in some way himself, but the Doctor angrily denies this, calling him "a distortion of me! A diminished, shrunken parody of me!", stating that he will always be a lesser creature since he is only the darkest sides of the Doctor. Genesta points out that he has still beaten the Doctor, as he has no options left. But the Doctor refuses to give up, and tells Genesta that though she reminds him of himself, she doesn't know him yet, and he plans to rectify that once he has solved this problem. He tells her that they need to use her TARDIS again, promising her to show her the universe once it is all over. Genesta gleefully agrees.
Weakened, the Doctor plots a course. He travels back in time to find his own TARDIS in mid-flight in the Time Vortex. Avoiding being detected, he uses the scanner to check if he found the right moment. On the screen he sees his past self and Mel discussing the Lakertyan System. The past Doctor says to Mel that they are not going there, since he has detected radiation in that system of a kind there is distinctly unhealthy to humans and outright deadly to Time Lords, so he suggests they go to Zastros 8 instead for a computer science conference, which Mel agrees sounds like a good idea. The present Doctor points out that the Nathemus already at this point started interfering with his TARDIS, causing him and Mel to go to Zastros 9 instead of 8. The Doctor says he needs to access the telepathic circuit of Genesta's TARDIS. She asks why, and he explains he needs convince his past self to change course, but just landing this TARDIS inside his own and telling himself is a bad idea; he needs to do something more subtle, like giving his past self a telepathic message. Genesta asks if a slight change of destination is really going to change anything, and the Doctor states that it might just save his life. Genesta tells him to go ahead, and the Doctor sets the TARDIS to travel a couple of minutes back in time, so he can send the message at the right moment. Genesta suddenly starts laughing at length, prompting the Doctor to ask her what it is that is so funny. "You. What does it matter if you go to Zastros 8 or 9," she says "or 1, 2, or 3 for that matter? This is so typical of you; petty pointless tampering." The Doctor replies that he doesn't understand "You never do, Doctor, do you?" she says as she transforms into the Valeyard.
Despairingly, the Doctor asks him how long he has been pretending to be Genesta. Valeyard asks him if it really matters, and the Doctor says that it matters to him, but the Valeyard doesn't care. The Doctor begs him to just say that he wasn't her from the start, but he replies that all he needs to know is that he enjoyed it; he relished in teasing the Doctor with the belief that not all hope was lost, that he could still somehow survive. "I'm not dead yet!" the Doctor spits back, as he keeps working the controls. He states that he refuses to believe that Genesta was him all along; she had too much life in her unlike the Valeyard, who the Doctor denounces as "a shadow." "A shadow that is about to cast itself over the whole of Time Lord history!" the Valeyard replies. The Doctor states that he will still try to do one last bit of interference, and the Valeyard casually and mockingly lets him, telling him that he doesn't believe it will make any difference any way, telling him he has already lost and his minute is up. But determined and undeterred, the Doctor manages to send a message to his past self.
Mel asks the past Doctor about the place he didn't want to go to, just as he receives the message from his future. Mel notices that the Doctor looks very vague all of a sudden, like "someone walked over your grave." "You know, it did really feel very much like that," the Doctor replies darkly.
Basking in his triumph, the Valeyard gloats that the Doctor's time is up and he will be going back to the Matrix to face his final erasure. The Doctor replies that he is indeed going that way, but not like the Valeyard thinks and starts to laugh. Confused, the Valeyard asks the Doctor what he means. The Doctor answers that the Valeyard's certainty is amusing; he knows that the future is always uncertain. For instance, he doesn't know the source or form of the deadly radiation in the Lakertyan System or who is responsible for it, but he knows that if he goes there, it will almost certainly kill him. Worried, the Valeyard asks what that would achieve, and the Doctor replies that he has realised that the Nathemus cannot exist without his unique mind; once he is gone they will wither and die from starvation, thereby ending the Valeyard's power over the Matrix. "But what if you regenerate?" asks the Valeyard. The Doctor says that he indeed hopes he regenerates, pointing out that when he does, the cells of his body and mind will be brand new, so the Nathemus will not have any connection with him. Either way the Nathemus will die and the Valeyard will be stuck in the Matrix with nowhere to go.
Just then, both the Valeyard and the Doctor are dragged back into the Matrix. Frightened and cold, the Valeyard calls out for the Doctor, telling him that he has killed them both and robbed himself of a future. "A future as you?" says the Doctor, "That's no future at all." The Doctor then starts to reminiscence about the life he led, and the Valeyard asks him bitterly to spare him that. The Doctor answers that he won't spare him, as he would have ended both the Doctor and Time Lord society without a second thought if he had not been stopped: "Frankly, I will die happy if the last words you ever hear are mine. Words in praise of the best of times: Peri, Mel, Evelyn, Flip, Mila, Constance, and all the others!" "And yet, you'll leave Mel to die in your TARDIS?" the Valeyards ask accusingly. The Doctor replies that he knows that the radiation is lethal to Time Lords but not to humans; in the end, Mel and Time Lord civilisation will survive even if he himself will not, and he considers this comfort enough. The Valeyard then desperately shouts that the Doctor can't just let him die as he is a part of him, but the Doctor replies that the Valeyard is nothing to him. "What about your precious moral scruples?!" the Valeyard asks. "They died with me," says the Doctor.
Inside the TARDIS, the Doctor shouts for Mel to hold on to something, as they are being attack by focused beams of radiation from the planet of Lakertya. The Doctor wonders how he missed the readings and says he doesn't understand why this is happening; the Lakertyans are known to be a peaceful people. The TARDIS starts taking damage, and Mel worried asks him just how deadly the radiation is, but the Doctor ensures her that she will be alright, but she starts losing consciousness, collapsing onto the floor of the TARDIS, as the Doctor laments that he didn't have time to tell her that the radiation is only deadly to Time Lords.
The Doctor, realising what is going to happen, accepts his fate with a sigh and a melancholy "Oh, well..." Collapsing to the floor while groaning in pain, he manages to gain enough composure enough to say some last words: "I've had good innings. All those lives I have lived... I hope the footprint I leave will be... light, but apposite..." But suddenly, he hears a soft voice, touched by a slight Scottish blur, telling him: "It's far from being all over." Asking who said that, the Doctor faintly spots a strange figure, before losing consciousness as he begins to regenerate.
Back in the Matrix, the other Doctor can feel the shift in his timeline and realises what is happening to him. "Yes, I will regenerate," he states, as he begins to change into his next incarnation, repeating what he just said in the voice of the next Doctor. In unison, both voices state, "Our future is in safe hands," before fading away.
- The Doctor - Colin Baker
- Melanie Bush - Bonnie Langford
- The Valeyard - Michael Jayston
- Genesta - Liz White
- Coordinator Storin/Nathemus 1 - Robbie Stevens
- Lorelas/Nathemus 2 - Susan Earnshaw
- The Seventh Doctor - Sylvester McCoy
- Zastros 9 is a hostile totalitarian state planet policed by flying lizards.
- Zastros 8 is a peaceful world and free-thinking paradise, with sunshine, seas, beaches protected from ultraviolet light and computer sciences.
- This story was recorded at The Moat Studios.
- The unofficial charity novel Time's Champion bears some similarity to this story, as it also featured the Sixth Doctor's final battle with the Valeyard leading to his regeneration. Additionally, a story of the Valeyard taking the Doctor's place besides Mel was explored in the alternative universe story He Jests at Scars...
- Another account of the Sixth Doctor's regeneration posits that his death was a result of being weakened by absorbing chronon energy in the Spiral Chamber. (PROSE: Spiral Scratch)
- The Sixth Doctor is the second Doctor to have the circumstances of his regeneration explained in spin-off media rather than a television story, the previous being the Second Doctor, whose regeneration was seen in the comic story The Night Walkers.
- Like with the Eighth Doctor's regeneration, this was explored years after the actor (Colin Baker) was replaced in the role on television.
- While regenerating, the Doctor briefly interacts with his successor. A similar notion had been depicted in the fan film Devious, with Jon Pertwee's Third Doctor appearing as an apparition to Tony Garner's regenerating "Second-and-a-Halfth Doctor".
- This story bears strong similarities to former script editor Eric Saward's original vision for the ending of the 1986 serial The Ultimate Foe, as originally envisaged by Robert Holmes before his passing, which was never produced due to his quitting work on the series after a fallout with the show's executive producer at the time, John Nathan-Turner. Had it been allowed featured, the ending would have seen the Sixth Doctor and the Valeyard locked in combat within the Matrix in a climactic struggle for their lives and ending on a cliffhanger; however, at the time, the series was in danger of cancellation, and Nathan-Turner argued against its use because it was presented in a way that suggested this could become the Doctor's ultimate fate, and therefore could be used as an excuse for cancellation. Here, similar events take place, but the Sixth Doctor is confirmed to escape confinement in the Matrix when he regenerates, while the Valeyard is left in a state of limbo inside the Matrix, unable to get out, with his ultimate fate unknown.
- The climax of this story provides a startling explanation for the Doctor's transformation into a much more dangerous man once he regenerated into his seventh incarnation, and by extension, the escalating aggressiveness of who he is at heart as he ages. When the Valeyard questions the Sixth Doctor's "precious moral scruples" as a reason to stay alive, he replies, "They died with me". Essentially, after being backed into a corner by the Valeyard, he has decided to let go of his moral restraints and realise a darker side of himself to properly combat more dangerous enemies so he could avoid a situation like this from happening again, because the Valeyard took advantage of both them and his good nature. This heavily foreshadows the Doctor's drastic, possibly even severe, shift in personality upon becoming the Seventh Doctor and growing out of his initially lighthearted and comedic demeanour, whose actions are far less restrained or made to hesitate by morality (such as the Fifth Doctor, who predated the Sixth, being tethered down and at times left indecisive by morality, but the Tenth Doctor, a much later incarnation, refusing to offer second chances to those who crossed him once, as well as the intensely pragmatic and drastic Twelfth Doctor), making him much more dangerous and manipulative, as well as taking the initiative against prospective enemies by actively seeking them out before they can expand their reaches. This also foreshadows a marked increase in his ruthlessness and the moral ubiquity of his methods. Ironically, later incarnations would continue growing darker and bear close similarities to the Valeyard, showing that through this sacrifice, the Doctor has risked becoming the very thing he has tried to avoid changing into.
- This story technically marks the first chronological appearance of the Seventh Doctor. His first words spoken are, "It's far from being all over."
- In the accompanying commentary disc for The Sixth Doctor: The Last Adventure, Nicholas Briggs notes that in writing this story, he found it strange that the Doctor would travel to Lakertya if there was a danger implied to be present nearby, and thus wrote an explanation behind his arrival at the planet.
- The TARDIS travels to the Lakertyan system. (TV: Time and the Rani)
- The Sixth Doctor says "I've had a good innings". This is one of the lines spoken by him in his alternate regeneration account, Spiral Scratch. The Twelfth Doctor would also mirror this statement when faced with the prospect of his own death. (TV: Before the Flood)
- The Sixth Doctor's final words are "Our future is in safe hands", spoken in unison with his successor. The Doctor previously said a similar phrase in his first incarnation, and would later say it again in his tenth incarnation. (TV: The Five Doctors, The Day of the Doctor)
- The Doctor toasts the companions of his incarnation: Peri, Mel, Evelyn, Flip, Mila, Constance and "all the others". The Eighth Doctor would do the same thing prior to his regeneration. (TV: The Night of the Doctor)
- While in the thralls of regeneration, the Seventh Doctor tells his predecessor that it is "far from being all over". (TV: The Tenth Planet)
- The Sixth Doctor is the second of three incarnations of the Doctor to perish from severe radiation exposure, and also the second to die in an act of self-sacrifice. The Third Doctor let himself be exposed to radiation from a large concentration of Metebelis crystals to seek audience with the Great One and eventually succumbed to it after ten years of being stuck in the Time Vortex while unable to pilot the TARDIS in his deteriorating condition (TV: Planet of the Spiders), and the Tenth Doctor would later put himself in the path of 500,000 rads when Wilfred Mott could not escape a booth about to be filled with radiation unless the Doctor switched places with him to unlock the booth from inside the machine when touching any of the controls would set off the radiation. (TV: The End of Time)
- The Sixth Doctor's choice to avoid going to Lakertya but ending up going anyway, resulting in his death and regeneration, parallels how the Eleventh Doctor wished to avoid Trenzalore when he learned of a prophecy about his downfall occurring once he went there, but eventually chose to, remaining on the planet for so long he began ageing to death before being granted a new regeneration cycle by the Time Lords. (TV: The Name of the Doctor, The Time of the Doctor)
- The Doctor remembers his companion Charlotte Pollard as Mila. (AUDIO: Blue Forgotten Planet)
- The Doctor gives up the values of his current life in order to make a sacrifice for the greater good of the universe and regenerate into a more capable and dangerous individual. This would later happen in a considerably worse degree when the Eighth Doctor sacrificed the name of "the Doctor"- not just sacrificing his own values, but the ones he carried across all his previous lives- so he could regenerate as a warrior, becoming the War Doctor. (TV: The Night of the Doctor)