Enjoying a holiday in the sun, Mr and Mrs Fergusson are relaxing on board a chartered yacht off the coast of France - their only crew, the skipper-owner and his adopted daughter. On taking a turn around the deck, Mr Fergusson is rather put-out to discover a stowaway helping himself to the comforts of their dinghy. Though very charming, the stranger refuses to give any explanation for his presence - and the Fergussons soon find themselves involved in a rather more eventful sailing trip than they had expected!