UNIT are called in when top secret plans and valuable equipment is stolen from high security establishments. The newly regenerated Doctor suggests that the thief may not be human.
Using the deadly disintegrator weapon, the robot steals the destructor codes. Harry Sullivan is sent to infiltrate Think Tank to discover the truth.
Sealed inside an underground bunker, Miss Winters issues her demands to the world's leaders, threatening a devastating nuclear strike if her demands are not met.
The Doctor races to avert a nuclear holocaust. The robot, distraught over killing its creator, takes Sarah hostage and goes on a rampage.
