The Doctor and the newly formed UNIT must stop a Cybermen Invasion and a Sinister Industrialist in league with them

The Doctor and Jamie are taken prisoner by their mysterious observers and have a reunion with an old friend while Zoe and Isobel carry out their own investigation of IE.

The Doctor and Jamie return to the IE factory in search of Zoe and Isobel, where they meet with Professor Watkins and fall foul of Vaughn.

Captain Turner manages to rescue Jamie and the others, while the Doctor begins working on a way to protect everyone from the Cybermen's hypno-sound signal.

The Cybermen have launched their deadly megatron bomb which will destroy all life on Earth unless the Doctor can deactivate the homing signal.