After holidaying in Ireland, Peter Weston (Donald Sinden), a London music department sales clerk and aspiring songwriter/musician, meets Irish lass Moira O'Shannon (Jeannie Carson) aboard the overnight sailing back to England, and attracted to her, offers her a ride back to London once they dock, which she accepts. His attraction to her is despite he already being engaged to Vanessa Colebrook (Diana Dors), the daughter of wealthy Sir James Colebrook (James Robertson Justice), Peter himself not coming from wealth which may be an issue for Sir James. Peter's attraction to Moira to some extent doesn't matter as Moira too is already engaged, her fiancé Albert currently working in South America. By the time Peter and Moira are ready to disembark the ship, Peter has reluctantly inherited something: a live alligator named Daisy, albeit a tame one. While Peter, who in general is scared of reptiles, wants to get rid of her in any way he can, Moira does whatever she can to ensure he doesn't, she an animal lover in being an animal keeper at the London Zoo.