Prisoners of Fate (audio story)

Prisoners of Fate was the one hundred and seventy-fourth story in Big Finish's monthly range. It was written by Jonathan Morris and featured Peter Davison as the Fifth Doctor, Sarah Sutton as Nyssa, Janet Fielding as Tegan Jovanka and Mark Strickson as Turlough.

Publisher's summary
Twenty-five years ago, with Richter's Syndrome running rampant throughout the galaxy, the brilliant biochemist Nyssa, formerly of Traken, made a painful farewell to her young family... and set off into the space, in search of a cure for this deadly disease.

She never returned.

Now, her grown-up son continues her work on the penal colony of Valderon, still desperate to make the breakthrough that eluded his presumed-dead mother.

So when the TARDIS lands on Valderon, bringing the Doctor, Tegan, Turlough and Nyssa to its fortress prison, the scene is set for a painful reunion... but not only for Nyssa. The Doctor's past is about to catch up with him too...

Part one
The Doctor, Tegan, Turlough and Nyssa land on a colony in the year 3556 due to the TARDIS being brought there by a signal. They meet Sibor who explains to them about the chronoscope and that their planet Valderon is governed by the predictions of the chronoscope and that people are arrested before they commit the crime. She also explains that the planet is in quarantine as it is a place for researching a treatment for Richter's syndrome, and the prisoners on the planet are used as scapegoats for testing cures. They are greeted by Galen (really Adric Traken, who uses the pseudonym as he saw his mother earlier and mistakenly thinks that he is meeting her at an earlier point in her life before she stayed on Terminus and uses the name to avoid a paradox that his mother would often warn him about), who is a researcher and asks to speak to Tegan privately since she is carrying biomes and microorganisms not seen for thousands of years. Once alone, Adric reveals the truth to Tegan. Tegan, immediately realising the consequences that Adric thinks it's an earlier point in time and asking for them to save his mother, creating a paradox as she will have never left Terminus in the first place. She informs the Doctor of the situation who realises the severity and proceeds to get everyone back to the TARDIS and get away as soon as possible, despite earlier being intrigued by the chronoscope and being reminded by Turlough that they'd come to investigate the strange signal picked up by the TARDIS. Angered at never being trusted, Turlough storms off to go talk to Adric. Turlough tells him the truth not knowing the severity and Adric becomes angry at his mother seemingly having left them to travel.

The Doctor tries to get Tegan and Nyssa to the TARDIS but Tegan tells Nyssa and they are then found by Sibor, who brings them back to see Adric, and leaves them alone. Adric asks to speak with Nyssa privately and reveals to her he knows and tells her about her own future, in doing so sealing Nyssa's fate and never allowing her to return to the time just after she disappeared, ensuring that the cure for Richter's syndrome she discovered is not found earlier, Lasarti, her husband, dies ten years before, alone, and Neeka becomes infected. The Doctor suspects he has told her everything behind closed doors but just then Sibor arrives with armed guards to arrest Tegan and Turlough as the chronoscope has just predicted they will commit murder by killing a watchman to make their escape and the Doctor realises the problem...

Part two
Nyssa and Adric talk about what happened over the past 25 years since she was declared dead after going missing (really ending up joining the Doctor again) and realise that they both have the other part needed to create the cure for Richter's syndrome. They prepare to create the cure but are interrupted by Mahandra who informs them that Sibor has arrested Tegan and Turlough. The Doctor, meanwhile, tries to defend them at their trial but loses and the two are locked up. Nyssa angrily confronts the Doctor and berates him for the choices he made and keeping information from her. Tegan and Turlough start to hear voices in the prison, while Nyssa, in the process of preparing a vaccine for Richter's syndrome, also hears the voices which takes the Doctor's attention away from finding a way to get Tegan and Turlough out. The cure is successful but Sibor arrives and arrests Adric, saying that she plans to use the cure they have just developed as a leverage against the Earth Empire in order to become prime designate.

The mysterious voice draws Turlough out of the prison and Tegan and Kartis (a wrongly accused convict from earlier) follow him until he finds a mysterious white cabinet in the center of the prison. Meanwhile the voice reaches out to Nyssa while she, the Doctor and Mahandra attempt to get into the prison to save Tegan and Turlough and in the meantime Adric escapes the alcazar and attempts to make contact with the Earth Empire to let them know they have found a cure. However his message gets completely scrambled into incomprehensible languages while Mahandra explains "Miracle Day" to the Doctor as they search the prison, how one day everyone on the planet suddenly woke up and were able to understand every possible language. They eventually find Tegan who has been knocked out by Turlough as he attempts to wire up the "cabinet" to give it power. Just then it sends out a telepathic field that knocks almost everyone except the Doctor unconscious and to his horror, it takes control of Tegan and Turlough and reveals itself to be the source of the chronoscope as Adric is captured by Sibor, and it reveals itself to be the Doctor's first TARDIS, his type 50 TARDIS...

Part three
The Doctor's type 50 reveals how it barely managed to escape Gallifrey and crash-landed on Valderon, where Sibor found it and realising its potential kept it trapped and used it as the chronoscope. However, it reveals that it was actually part of its plan and explains how it managed to lure the Doctor here and expresses its desire to have the Doctor return it home. The Doctor agrees but only if it releases Turlough and Tegan from its mind control which it does. He then shuts off its power and assures Turlough he'll keep the promise but would prefer to have it relieved of power.

Sibor, who has found out about what's going on, takes Nyssa and Adric hostage and finds the type 50 TARDIS, and hooks it back up to its power source from the planet's power supply but ends up getting electrocuted in the process. It then seemingly dematerialises. Nyssa finds the Doctor and explains everything and they are soon joined by Tegan and they return to the TARDIS to try track the type 50. However, it is revealed that the Tegan with them was merely the type 50 TARDIS using its still-functioning chameleon circuit to disguise itself. It then puts the TARDIS in a temporal state of grace and captures Nyssa and the Doctor. It brings Nyssa back to 3531 in an attempt to change the timeline and offers Nyssa a chance to watch her children grow up as she had missed when she began traveling with the Doctor again and was presumed dead. The Doctor tries to stop her, citing the irreparable damage she will cause to the timeline but she cannot restrain herself and departs. The Type 50 then "eats" the Doctor's TARDIS's dematerialisation circuit and leaves, stranding the Doctor. Meanwhile, the real Tegan finds Turlough and Adric and they go to find the Doctor, who explains the events that had just transpired. He explains that they have to stop the type 50 as it has now created two timelines and the results will be an explosion that could wipe out half the galaxy....

Part four
The type 50 materialises in front of Katris and Mahandra and takes on the form of the deceased Sibor and takes over their minds. Inside the TARDIS, the Doctor has Adric reach out to his mother in the past which is now altering the future using the TARDIS telepathic circuits to convince her not to go inside, and after finally getting through to her, manages to convince her to fly off-world to somewhere far-away and distant and have no contact with any of them for the next 25 years. The Doctor explains that this will stop the new timeline being created and stop the blinovitch limitation effect which the type 50 is using as an energy source to rebuild itself. The timeline stabilizes and they are able to finally exit the TARDIS without being destroyed by the effects which had hindered their earlier attempts to escape, and find Nyssa arriving on a shuttle, having had to wait out the 25 years alone and due to this has become bitter and resentful, especially of the Doctor.

They then confront the type 50 but discover that there is a paradox still keeping it alive: moments earlier, Nyssa had revealed to the Doctor that Galen is really Adric, her son and that she was contacted by the Doctor before he regenerated, and when she told him then she was a mother, he was extremely surprised, seemingly unaware, something from his future he should not have known about. The Doctor, however, realises a loophole: since Nyssa wasn't aware whether he actually really knew and was acting surprised, or really wasn't aware, he can do his best to feign surprise and still keep the timeline intact. The paradox resolved, the type 50 collapses, out of power and seeing nothing but its own demise. After talking with the Doctor, it has a change of heart and using its final power it helps the Doctor erase the 25 years Nyssa had to wait, partially re-setting the timeline, and the type 50 destroys itself, taking the paradox with it while a saddened Doctor and Nyssa watch on. Those possessed by the type 50 who were knocked unconscious slowly come to as well.

Cast

 * The Doctor - Peter Davison
 * Tegan Jovanka - Janet Fielding
 * Turlough - Mark Strickson
 * Nyssa - Sarah Sutton
 * Sibor - Sarah Douglas
 * Galen/First Watchman - Alastair Mackenzie
 * Mahandra/Maxis/Computer - Anjella Mackintosh
 * Kartis/Lasarti/Second Watchman/Patient - Jez Fielder

Continuity

 * Adric mentions his mother having talked to him about Omega (TV: Arc of Infinity), the Cybermen and his namesake (TV: Earthshock) and her visit to the 17th century. (TV: The Visitation)
 * Adric mentions his mother meeting Turlough on Earth, at Brendon Public School, with a Brigadier, and a creature called Mawdryn. (TV: Mawdryn Undead)
 * Turlough refers to Purity, (AUDIO: The Whispering Forest) Vektris (AUDIO: Kiss of Death) and the Sontarans. (AUDIO: Heroes of Sontar)
 * Turlough refers to Nyssa being rejuvenated by Homogenite. (AUDIO: The Emerald Tiger)
 * When the Doctor is discussing time-sensitive races who could possibly see into the future, he refers to the Tharils, (TV: Warriors' Gate) the Jagaroth, (TV: City of Death) the Xeraphin (TV: Time-Flight) and the Time Lords. (TV: The Deadly Assassin)
 * Nyssa tells the Doctor that she met him at a later point in his personal timeline while he was regenerating into his sixth incarnation. (AUDIO: Winter)
 * The Richter's Syndrome story arc that began in AUDIO: Cobwebs concludes in this story.
 * The Doctor would later speak directly to his Type 40 through an avatar during his eleventh incarnation. (TV: The Doctor's Wife)
 * The Doctor later echoes his first TARDIS's final words as he is regenerating, "Is this death?" (TV: The Caves of Androzani)
 * The Doctor believes that the reason that Turlough and Tegan were easily possessed by the Type 50 was due to their possessions by Eldrad (AUDIO: Eldrad Must Die!) and the Mara (TV: Kinda, Snakedance, AUDIO: The Cradle of the Snake) respectively.