Ian and Vicki are trapped by tentacled creatures on the planet Aridius. The Doctor and Barbara witness Daleks leaving Skaro on a mission to eliminate the Doctor and his companions.

The Doctor and his friends have been given shelter from the Daleks by the Aridians. But the Daleks threaten to kill the Aridians unless they hand over the time travellers.

The Daleks pursue the TARDIS through time and space. In an attempt to lose the Daleks, the Doctor makes a stop on the top of the Empire State Building and then on a sailing ship.

With the Daleks in pursuit, the TARDIS lands in what appears to be a haunted house. When the Daleks arrive, the travellers depart, not realising that they have left Vicki behind!

The Daleks follow the TARDIS to the jungle world of Mechanus, infested with lethal plants. There, the Daleks release a robot double of the Doctor that is programmed to kill.

The Doctor and his friends are taken prisoner by the Mechonoids. There they meet fellow prisoner, Steven Taylor. The Daleks break into the Mechonoid city and a battle commences.