On his way home by boat from a holiday in Ireland, mild-mannered English gent Peter Weston bumps into fiery Irish redhead Moira O'Shannon and takes an instant shining to her. Unfortunately, he happens to already be engaged - to the only daughter of a rich and powerful press baron, no less - and she the same. Never the less, they strike up a bond that is soon to become very useful to Peter indeed.

Shown to a shared cabin, the next acquaintance Peter makes is a very drunk Irish sailor who has run away from his home and wife with his beloved pet, Daisy, after an argument that Daisy's presence had apparently caused. But after Peter falls asleep, he wakes to find the Irishman gone and Daisy left in his care - and Daisy just happens to be an alligator!

Raised by the sailor since she was a new-born, Daisy is tame but no less alarming in appearance than any other of her species, and although certainly not large by alligator standards, is somewhat bigger than the average pet! Peter is none too amused by the imposition and makes off to dump her overboard and back into the sea, where he bumps into Moira again: and she reveals herself to be a London-based zoo worker who cannot stand to see any animal mistreated.

Resolved to staying in Moira's good books by finding a proper, caring home for Daisy, the trio return to the capital. Unfortunately Peter quickly runs out of options: his grandfather wants her shot; the police want nothing to do with such a beast; customs think his declaration of an alligator is a joke; the zoo is full; and the proprietress of a pet shop insists she can speak to the animal, who is very happy to be living with such an attractive young man as Peter and doesn't wish to go anywhere else, thank you very much.

Meanwhile, Peter and his parents are due to visit the country home of his fiancée Vanessa's father to formally meet for the first time, hold a gala engagement party, and finalise details between the two families of the pair's impending nuptials. Still stuck with Daisy and needing to give her regular baths lest she dry out, Peter sneaks her along for the trip; but when she manages to find her way into the packed ballroom, pandemonium understandably ensues!