The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.

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.