The Daleks and the Cybermen form an alliance to kidnap the American Envoy and ruin a peace conference on Earth. The Doctor meets a new companion, a Frenchman called Jason. After they fail to stop the Cybermen taking the US Envoy from a nightclub, they are joined by a singer named Crystal who works there. After a trip to Altair Three and then the Bar Galactica, they meet Madame Delilah but are forced to flee along with a small furry creature called Zog.

The travellers are captured briefly by the Daleks. They navigate the ship through an asteroid field before making a series of short trips, then confront the Dalek Emperor. The Doctor tricks the Emperor into revealing that the Daleks intend to betray the Cybermen and a battle breaks out between the two. Returning to Earth, the Doctor realises the US Envoy is under Dalek influence and programmed to destroy London with a Dalekanium bomb. The Doctor breaks his conditioning and defuses the bomb by putting it in a teapot.