The Doctor is sent to Planet Chronos to find and bring back several survey mission teams that have vanished into thin air. Accompanied by his mature and loyal companion Dr Evelyn Smythe and a third survey crew, the team are close to solving the mystery, when a member of their gang mysteriously disappears. The Doctor realises that these disappearances are far more serious than they thought. The Cybermen couldn’t possibly be behind these strange goings on...