Whilst The Doctor, Steven and Vicki are traveling to their next destination. On the planet Kembel, Marc Cory, a Space Security Service agent discovers The Daleks are attending a secret meeting with their allies. Where Cory discovers the Dalek's evil plan, which sets the stage for the epic 12-part adventure "The Dalek Master Plan".

In 1986 a new planet appears in the Solar System which turns out to be a long-lost twin of Earth's named Mondas. Its inhabitants are the Cybermen.

As the newly-regenerated Doctor arrives on Earth, so does the Nestene too.

UNIT's attempts to locate the meteorites are hampered by the mysterious plastic Autons, being constructed by Channing at a nearby factory, while the Doctor makes another attempt to escape from the hospital.

Ransome manages to escape from the plastics factory and alert UNIT, prompting the Doctor and the Brigadier to start an investigation.

With UNIT's investigation being blocked by the Replica of Scobie, the Doctor and Liz visit Madame Tussaud's to try and find out more as Channing prepares to activate the Autons.