The travellers arrive in a strange domain presided over by the Toymaker (Michael Gough) - an enigmatic, immortal entity who forces them to play a series of games, failure at which will render them his playthings. The Doctor has to solve the complex Trilogic game while Steven and Dodo are faced with defeating a succession of apparently child-like but potentially lethal animated toys (Carmen Silvera, Campbell Singer, Peter Stephens) in contests such as blind man's buff, musical chairs and 'hunt the key'.

The Doctor finally overcomes the Toymaker by imitating his voice in order to complete the Trilogic game from within the TARDIS, which then dematerialises as his foe's universe is destroyed.

_{Synopsis from Doctor Who: The First Doctor Handbook by David J. Howe, Mark Stammers and Stephen James Walker, reprinted with permission; further reproduction is not permitted. Available from Telos}