Dr. Simon Sparrow's love life improves dramatically when the lovely Delia Mallory is brought into casualty with a sprained ankle. She's relieved at the diagnosis as she is a model and is as attracted to Sparrow as he is to her. Sparrow finds himself treating Sir Lancelot Spratt who has taken to sleep-walking. He has also quite suddenly lost his gruff manner and is being quite nice to everyone. Sparrow quickly diagnoses Spratt's condition: he's fallen in love. The object of his affection is physiotherapist Iris Merchant. Sparrow urges him on but she also has another suitor in the form of Major Tommy Ffrench. Spratt tries to hire a private detective to follow her but when that doesn't work out he takes to following her himself. Mayhem ensues.