Secrets of Telos

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?