Part 1
The Doctor wants to know why the Brigadier has called him back.

Part 2
Harry meets Broton, War Lord of the Zygons.

Part 3
The Doctor is taken prisoner by the Zygons.

Part 4
The Zygons think the Doctor is dead after he is electrocuted by the communications system.

Cornered by a Zygon
Zygon leader Broton wants the Doctor destroyed. Meanwhile, Sarah telephones the Doctor from the infirmary where Harry has been taken to recover from his head wound. Their conversation is interrupted as Sarah is attacked by a Zygon!

Credit: BBC Worldwide