Going nowhere fast, Billy Fisher, an incorrigible fantasizer, dreams incessantly of escaping his drab existence and humdrum routine work as an undertakers' clerk in Yorkshire. Seeking refuge from his working-class family and not one but two demanding fiancees in the imaginary country called Ambrosia, more and more, Billy finds himself cut off from reality, picturing himself as its ruler and hero. Then, as Billy's fabrications grow increasingly wilder and problems start piling up, lovely, happy-go-lucky Liz enters the young day-dreamer's life, offering a way out of this fine mess. However, new beginnings are always scary, and Billy must make up his mind: it's either a fresh start in London or an endless beautiful lie in Ambrosia.