When two belligerent Dominators and their robotic servant Quarks land on the peaceful planet Dulkis planning to drop a radioactive seed into the planet's core to refuel their spaceship, the Second Doctor, Jamie and Zoe must attempt to inspire the pacifist Dulcians to resist.

Blinker, so named because he blinks whenever he has a bright idea for a new invention, is the son of an eccentric Professor who is developing a top secret Pulsar Crystal X. Blinker's inventions help him to be a successful goalkeeper and to keep an eye on The Masons gang - and some real crooks.