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?

Plot
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.

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 mentions he's stumbled out of the TARDIS to find a body before.