The Brink of Death (audio story)

 was the last full cast audio story in the The Sixth Doctor: The Last Adventure audio anthology released in 2015 by Big Finish Productions. 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 on performed media with the original actors, and the second attempt overall, following 2005's Spiral Scratch.

Publisher's summary
The Doctor and Mel face the final confrontation with the Valeyard - and the Doctor must make the ultimate sacrifice.

Plot
Mel, riding a battery-powered vehicle comparable to a skimmer, is attempting to escape a group of monsters. 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 monsters are able to get a hit on the vehicle's engines, causing its battery to start dying which enables to catch even more up to Mel. The Doctor, unable to teleport Mel back to the TARDIS, instead teleports himself in the "skimmer" and set off the ejector seats, which used retrorockets to land them safely next to the parked TARDIS. Mel asks him if that was also part of the plan, but the Doctor says 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 ensures 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 tells her that her service records are already contains several reprimands regarding her attitude and 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, as he was standing in his TARDIS a mere few moments ago. Genesta suggest that 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 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's 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 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 Doctor. The Doctor asks if he can have a look, and immediately recognizes the person on the screen as the Valeyard.

more to be added.

Cast

 * 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

Planets

 * Zastros 9 is a hostile planet full of monsters.
 * Zastros 8 is a peaceful world, with sunshine, seas and computer sciences.

Continuity

 * The TARDIS has previously travelled through 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 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 will 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 similar prior to his regeneration. (TV: The Night of the Doctor)
 * While in the thralls of regenerating, 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 because it was 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 needed to, remaining on the planet for so long he began dying of old age and regenerated with the help of 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)