The TARDIS arrives on the planet Dulkis where the Doctor, Zoe and Jamie decide to have a quiet holiday. Only to find the Evil Dominators and their robotic slaves, The Quarks have arrived on a radioactive island, where they plan to detonate a bomb in the planet's core, which will turn the entire planet as source of radioactive fuel for their invasion fleet.

Zoe and Cully are captured by the Dominators and put to work alongside the survey team while the Doctor and Jamie decide to return to the island to help.