The Doctor's time-travelling machine is trapped in the flight-path of an alien spacecraft in orbit around the Earth. To avoid the fatal impact of a head-on collision the TARDIS resorts to the only escape possible and materialises on board the on-coming liner.

This solves the immediate problem, but a new difficulty arises — the TARDIS cannot get off the ship until a radio signal transmitting from Earth has been disconnected.

The Doctor sets off in a Transmat Capsule, having programmed the TARDIS to enable Tegan and Nyssa to follow him once he has dealt with the interference.

Naturally enough, things don't go quite as planned...

Novelization of the Doctor Who TV series; four episode story "Mawdryn Undead" (1983), script by Peter Grimwade.