Having been encouraged to take up jogging by his wife Hilary, Brian sees his girl-friend, Wendy, in his friend George's flat when he is ostensibly running around the park. However, while Brian is visiting Wendy, helpful George knows that his own affair will not be discovered as the object of his affection is Brian's wife Hilary! It is all plain sailing until George's wife Jessica returns too soon from a business trip to America ...