The End of the Line (audio story)

 was the first story in the audio anthology The Sixth Doctor: The Last Adventure, produced by Big Finish Productions. It was written by Simon Barnard and Paul Morris and featured Colin Baker as the Sixth Doctor, Miranda Raison as Constance Clarke and Michael Jayston as The Valeyard.

Due to the anthology having its release date pushed forward, it was the first audio released to feature the Doctor's companion Constance Clarke, before her actual debut story was released.

It saw the second time both the Master and the Valeyard have been involved in the same story in a performed production, the first being 1986's The Trial of a Time Lord arc.

Publisher's summary
The Doctor and his latest companion Constance investigate a commuter train that has lost its way...

Plot
Lost in the fog on a railway, Tim Hope, a traveller, stumbles across the Sixth Doctor and Constance Clarke, who are themselves stranded on the same railway, unsure where and when they are. Tim tells them that he and other passengers are stuck on a train not far away; him and his fellow travellers have come down from the train to go around and try to understand where they are. The Doctor and Constance ask Tim to lead them back where his train is.

The three reach the train, only to find him abandoned and ravaged. They once again leave, worried about the fate of the passengers, and come across Keith Potter, a trainspotter. He tells them that he saw the railways growing in number as he observed, and joins them in their search for the train. The four of them see a train very similar to the one they left, to the point of having on board Tim's travelling companions, who leads them to the conclusion they must have found another train, of a similar model.

Aboard the train, things are far from quiet. Norman, the controller, does not allow anyone to leave, and Hilary, one of the passengers, says she found another of her companions, Dave, dead outside the train. The Doctor suggests they check on the driver, but when he, Tim and Constance do, they found he is missing and the windows of the drive cabin are smashed. As they report this to the passengers, a man knocks on the door of the train, asking to come in: to everyone's amazement, everyone recognises him as Dave, the passenge Hilary found dead. The Doctor insists they open the door, but Norman and the other passengers stop him from doing so, leaving Dave to die at the hands of something out there.

The Doctor reproaches them, but Norman manages to turn all the passengers against him and Constance; they move to lock them into the bathroom, but when they open the door, they found Dave's body in there. The discovery allows the Doctor time to think, and gather there must have been three Daves, all of them dead; he also stars suspecting about Hilary, the only passenger not to have an alibi, the only witness to see the body and the one with blood stains on their dress. Under pressure, Hilary confesses she killed Dave out of resentment and anger for her failures in life. She herself, however, is horrified at the thought; when Tim tries to calm her down, she hits him with some force, leaving him bruised but alive.

Hilary leaves the train together with Keith, who promises to take her to the station. When they are out, though, Tim stops her and "induces" her to tell her what really happened: there were voices, Hilary says, exploiting her frustration, driving her towards the killing. Satisfied, Keith breaks the contact and leaves her to die at the hands of their misterious assailants.

On the train, the Doctor realises they stand on a reality nexus, a point of convergence between parallel universes, who are collapsing one on each other: they have actually seen different version of the same train and passengers, and Hilary has been victim of the influence of a "dark" version of herself. The station they should be headed for must be a point of control, which the Doctor decides to try and reach, aided by Keith, now back to the train. Constance remains on the train, together with the other passengers, but she is forced to leave with Tim after another passenger, Alice, is driven insane as Hilary, and attacks Norman killing him.

The Doctor and Keith reach the station, and find another version of Norman, with a different uniform; the station is built with a style which reminds the Doctor of the work of the Parallel Sect, an old species capable of moving through parallel universes. They designed this place as a control room, with the purpose of keeping up the shields between the universe, and also created the Normans (a species of robots) so that they act as caretakers. Here Keith reveals himself to be an avatar of the Master: he has taken control of the Normans and ordered them to disable the shields, thus allowing him transit in any dimension he wishes. However, to avoid dimensions to collapse, he has to introduce a safety protocol, which would heavily damage him: he intends to force the Doctor to do it for him.

Constance and Keith reach the station, and trick the local Norman to go and look for other versions of the passenger as they move on; short after, though, Tim is forced to stay behind because he feels himself attacked by his dark self. Constance enters the station and sees the Doctor confront the Master; the latter one immediately threatens her with the Tissue Compression Eliminator, thus forcing the Doctor to agree to his terms. However, the Doctor convinces Norman to revolt against the Master, noticing that the orders he is giving him go against his original programming. Norman then reinstates the shields, initiating a process which could, however, destroy the station. To stabilise it, the Doctor would need a dimensional stabiliser - which Constance promptly find in Tim's jacket.

As the Master/Keith escapes, he is approached by Tim, who on his turn is revealed to be the Valeyard in disguise. He came her to restore himself after his last encounter with the Doctor, but the Master's intervention nearly cost him his life. Now, however, he is once again in shape, and he threatens the Master to leave and stop meddling with the Doctor and himself. When Keith protests, the Valeyard kills Keith before leaving. With the dimensions restored, the fog clears, and the Doctor and Constance come back to the TARDIS and leaves, despite not knowing Tim's real identity.

Cast

 * The Doctor - Colin Baker
 * Constance Clarke - Miranda Raison
 * Tim Hope - Anthony Howell
 * - Chris Finney
 * Alice Lloyd - Ony Uhiara
 * Norman - Hamish Clark
 * Hilary Ratchett - Maggie Service

Uncredited

 * The Valeyard - Michael Jayston

Worldbuilding

 * Constance mentions the TARDIS always getting lost.
 * The Doctor mentions Cartesian geometry, which involves 26 dimensions.
 * Parallel universes aren't supposed to meet, hence the word 'parallel,' but there are various points in the universe where the parallels collide.
 * There are other dimensions that, while they can't be called "evil" since that's too subjective, are nonetheless darker, but these darker dimensions are usually "safely" away from the nice ones.
 * The Normans are "Normal Animates," since "normality" can have various meaning in different realities. They were grown by the Parallel Sect.
 * The longer the dimensional barriers are broken, the more dimensions collapse into infinity with accelerated "normative entropy".
 * The Master uses his TCE.
 * The Master's TARDIS is disguised as a ticket machine. The Doctor notes to Constance that the Master's TARDIS, much like the Master, is a "master of disguise".
 * Keith Potter is an avatar, operated by the Master from the safety of his TARDIS.
 * The Valeyard claims the dimensional nexus point as his domain, where he's been re-invigorating.

Continuity

 * Constance was a WREN during World War II. (AUDIO: Criss-Cross)
 * The Doctor refers to his darker self who he knows is still out there, despite trying to rectify the matter. (AUDIO: Trial of the Valeyard)
 * According to Norman, the Master has been referring to himself as the "definite article". The Fourth Doctor once referred to himself in the same way when it came to doctors. (TV: Robot)
 * After his true identity is revealed, the Master says, "Oh, my dear Doctor, you have been naive." He previously said this after revealing himself to the Fifth Doctor on 3 March 1215. (TV: The King's Demons)