Philip Markham, a publisher of childrens books, is asked by his business partner, Henry Lodge, if he can borrow the flat for the evening to gallivant with his latest girlfriend. As Philip and his wife will be out, he reluctantly agrees. At the same time, Joanna Markham is being persuaded by Linda Lodge to let her borrow the empty flat in order to entertain her lover. With some misgivings, Joanna agrees. What nobody knows is that the interior designer who has been decorating the flat for the past three months has decided that this is the night that he and the au pair girl will try out the new oval bed. When the Markhams evening out is cancelled, it is too late to let any of the parties know and three sets of hopeful lovers all converge on the bedroom at the same time. The situation is further complicated by the arrival of Olive Harriet Smythe, a straight-laced authoress of childrens books. The frantic efforts of the Markhams to hide the amorous goings-on and, at the same time sign up Miss Smythe, lead to a hectic and hilarious evening.