Somewhere outside space and time there waits the Celestial Toymaker, an enigmatic being who ensnares unwary travellers in his domain to play out his dark and deadly games. Separated from the security of the TARDIS, the First Doctor is forced to play the complex trilogic game with the evil magician. Meanwhile, Dodo and Steven must enter into a series of tests with, among others, the schoolboy Cyril and the King and Queen of Hearts.