Billy Fisher feels trapped by his working-class parents, his unfulfilling job as an undertaker's clerk, and his life in a dull, provincial town. His only refuge is in his daydreams, where he is the leader of the country of Ambrosia. Unfortunately, Billy's wild imagination leads him to tell lies constantly: to his parents, his employer, and his three girlfriends. On one tragi-comic Saturday, as Billy plots his escape to a life of adventure and excitement in London, all his lies finally catch up with him, with hilarious and disastrous results.