Secrets of Telos (audio story)

 was the first of two stories in the audio anthology Forty: Volume 1. It was written by Matt Fitton and featured Peter Davison as the Fifth Doctor, Sarah Sutton as Nyssa, Janet Fielding as Tegan Jovanka and introduced Christopher Timothy as Professor Parry and Ronan Summers as Captain Hopper.

Publisher's summary
Professor Parry's expedition to the tombs of Telos was hardly an unmitigated success. The handful of survivors limp home in a spaceship…unaware that the deadly peril they faced from the Cybermen is not yet banished.

Into this situation stumble the Fifth Doctor and his friends Nyssa and Tegan - and they're soon in a deadly fight for their lives.

Except things aren't quite that simple - something odd is happening to the Doctor. He's suddenly in a different part of his own timeline inhabiting his future self with no idea of why or how this has happened.

Who is bouncing him through time? And what could they possibly want?

Part one
Nyssa faints after leaving Monarch's ship and the Doctor experiences temporal dislocation, finding himself in his own future, not long after Tegan rejoined him and Nyssa. The TARDIS jumps along its temporal vector in search of a stable time track and materialises on a rocket and Nyssa attempts to find out what has happened without telling the Doctor about his future, explaining Adric's absence by saying that they recently parted ways with him. Upon exiting the ship, they find the unconscious form of Ted Rogers with a cybernetic attachment on his head.

The Doctor, Nyssa and Tegan are held at gunpoint by Captain Hopper and Morton. Hopper has Morton clamp the TARDIS and take Nyssa and Tegan in the hold whilst he and the Doctor, who remembers him from Telos, carry Rogers to the medical bay. The Doctor attempts to persuade Professor Parry of his identity before instead claiming that he is the Doctor's right-hand man, but Hopper handcuffs him when an alarm sounds and goes to investigate.

Parry releases the Doctor when he realises that Rogers is a victim of quickly-spreading Cyber-technology and they put him in a cryo-bay. The Doctor opens a cryo-bay containing a dead crewman and attempts to catch a Cybermat, but it eludes him and Parry and they fetch Hopper to show him the technology and prove that the rocket is in danger. They find that Rogers has disappeared, however; Rogers, partially cyber-converted, breaks into the hold and tells the chained Nyssa and Tegan that they will become like him.

Part two
to be added

Part three
to be added

Part four
to be added

Cast

 * The Doctor - Peter Davison
 * Nyssa - Sarah Sutton
 * Tegan Jovanka - Janet Fielding
 * Professor Parry - Christopher Timothy
 * Professor Vansom - Barbara Flynn
 * Morton - Tamzin Outhwaite
 * Captain Hopper - Ronan Summers
 * The Cybermen - Nicholas Briggs

Uncredited

 * Adric - Matthew Waterhouse

Medicine

 * Tegan is trained in first aid.
 * The Doctor states placing Rogers in cryo-sleep will slow the spread of the cyber-conversion.

Time travel

 * The TARDIS has jumped back along her temporal vector looking for a stable time track. The Doctor believes he's done the same and "infected" the TARDIS, having "skipped a time track" and been displaced along his own personal timeline due to being pulled along his time stream.
 * The TARDIS needs time to recalibrate.
 * Nyssa uses temporal telemetry to look for time distortion.

Planets

 * Earth is six weeks travel from Telos.
 * Telos Minor is a small planetoid with a jungle inhabited by beasts akin to six-armed bears. It has a cyber-factory connected to the tomb on Telos and with similar symbolic logic puzzles.

Cybermen

 * The Cyber-Army was at its height five hundred years ago.
 * Cybermats are always transmitting signals and are capable of replicating themselves, and repairing and sabotaging systems.
 * Cyber-Control on Telos Minor knows the Doctor is a Time Lord from Gallifrey.

Organisations

 * The Doctor refers to the Brotherhood of Logicians.

Individuals

 * Tegan and Nyssa are not aware of Jamie McCrimmon and Victoria Waterfield.
 * Tegan refers to her Aunt Vanessa.
 * Jim Callum and Ted Rogers were converted into Cybermen shortly after leaving Telos by a Cybermat who smuggled itself onboard Hopper's rocket.

Continuity

 * Captain Hopper and Professor Parry have just left Telos six hours ago. (TV: The Tomb of the Cybermen)
 * The Doctor recalls that Parry works with the Brotherhood of Logicians, hired Captain Hopper, and lost several men on the planet below. (TV: The Tomb of the Cybermen)
 * Just before the Doctor switches into his personal future, Tegan reminds Adric about the Urbankans. (TV: Four to Doomsday)
 * Nyssa suspects that Tegan's sudden return and the trouble with Omega may have caused the Doctor to forget their recent adventures. (TV: Arc of Infinity)
 * When the Doctor arrives in his future, Tegan and Nyssa attempt to avoid telling him about Adric's death. (TV: Earthshock)
 * The Doctor recalls the death of Klieg and Kaftan. (TV: The Tomb of the Cybermen)
 * Parry recalls Jim Callum being injured on Telos. (TV: The Tomb of the Cybermen)
 * Tegan recalls Cyber weapons having an affect on Cybermen. (TV: Earthshock)
 * The Doctor vaguely remembers John Viner. (TV: The Tomb of the Cybermen)
 * Nyssa recalls encountering several variants of Cybermen on her journeys. (TV: Earthshock, AUDIO: Spare Parts, Conversion)