Dr. Simon Sparrow's love life improves dramatically when lovely Delia Mallor is brought into casualty with a sprained ankle. As a model she's relieved at the diagnosis, and she's as attracted to Sparrow as he is to her. Meanwhile, Sparrow finds himself treating Sir Lancelot Spratt, who has started sleep-walking. He has also suddenly lost his gruff manner, and is being 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 has another suitor: Major Tommy French. Spratt tries to hire a private detective to follow her, but when that doesn't work out, he follows her himself.