The show's plot centred on the antics of a number of ghosts who worked for a firm called Rentaghost, which rented out the ghosts for various tasks.
The company, located in South Ealing, is run by Fred Mumford, a recently deceased loser who feels he can find work for ghosts whose lives were as failed as his. His first (and only) recruits are Timothy Claypole, a mischievous jester with a comical lack of knowledge about modern technology; and Hubert Davenport, a delicate Victorian era gentleman who is morally shocked by the modern world. The ghosts work from an office, which they rent from Harold Meaker, who discovers the truth about them in the third episode.
Over the course of several series, other characters were added: Hazel the McWitch, a Scottish witch; Nadia Popov, a Dutch ghost who suffers from hayfever and teleports away when she sneezes; and the pantomime horse Dobbin, who first appears in a one-off Christmas special called "Rentasanta" and is brought to life by Claypole, who is unable to cancel the spell afterwards – thus allowing Dobbin to remain in the show for the rest of the run.
Adam Painting, a local entrepreneur played by Christopher Biggins, frequently appears in episodes and tries, with limited success, to involve the ghosts in his latest business enterprise.