After possibly killing a man in a brawl at a farewell party Tony Gunther, an American merchant seaman, is knocked out and wakes up in the apartment of Laura Ring, the secretary of a shipping company.

Barbara Wright and Ian Chesterton, two humble teachers during 1963, discover a genius student's grandfather, simply known as "the Doctor", and his police box time machine. Deciding that the pair knows too much about his otherworldly origins, they are whisked away on a journey through time and space.