American performers Ben Lyon, his wife, Bebe Daniels Lyon, and their two children, Barbara and Richard, take temporary occupancy of a house they hope to lease in Marble Arch, London. Gaylord Hemmingway, the house's very fussy owner, is a writer who, under various pen names, has authored books on a wide variety of topics and is scheduled to sign off on the lease over dinner that evening. After Richard breaks one of the windows with his skis and a local handyman, Wimple, comes to repair it, Ben and Bebe hire a Scottish cook, Aggie MacDonald. However, as Aggie cannot start until the following day, Ben and Bebe have to prepare Hemmingway's dinner themselves and Wimple volunteers to help them. Unaware of their parents' plans, Barbara and Richard decide to hold a house-warming party that same evening. Preparations for the dinner become a disaster after Ben miswires the house's electrical circuits and Wimple states that the gas is not connected. At the moment of Hemmingway's arrival, Barbara, Richard and their friends burst in on their parents and initially horrify Hemmingway. Soon, however, the author reveals he has written a book about popular music and is a "hep-cat" and ends up danceing with the kids at their party. However, when an explosion wrecks the kitchen, proving that Wimple was mistaken about the gas not being connected, Hemmingway leaves dismayed. A day or two later, with the lease still unsigned, Ben and Bebe encourage Richard to date Violet, Hemmingway's daughter, to improve their situation. Barbara, meanwhile, concerned about her mother becoming a golf widow, attempts to interest her father in a new hobby by leaving a book about how to build a rock garden on his favorite chair. Suddenly, Ben becomes very enthusiastic and decides to build a garden, with a pond and fountain, in the back yard and begins by dynamiting the yard to break up the rocks. A cement mixer then arrives, followed by a plough. Violet, who is obsessed by horse riding, but also shows a healthy interest in Richard, assists Ben and Richard. However, as she empties a bag of quick-dry cement, a wind blows the contents over the men. Later, after geting herself cemented into the pond's base, Violet has to be extricated, and leaves angrily. Somehow, water intended for the pond and fountain ends up in the basement of the house. Later, after the garden is finished, Ben covers over the lily pond and fountain with sheets in preparation for a grand unveiling ceremony, to which he has invited Hemmingway. However, when Hemmingway presses the button to start the water flowing from the fountain, nothing happens. Instead the water begins to drain out of the pond, until Hemmingway investigates and it suddenly comes back on and soaks him. As Hemmingway leaves to call his lawyer, Ben discovers that Hemmingway, using one of his pen names, was the author of the rock garden book, whose instructions he followed. Later, when Ben receives a letter from Hemmingway, he does not open it, figuring that it is an eviction notice. The next crisis in the Lyon household is precipitated by Barbara, who announces that, within a few days, she will be marrying Slim Cassidy, an ice-skating, singing, movie star cowboy, who is currently appearing in London. Bebe asks her old friend, Florrie Wainwright, to try to talk Barbara out of the marriage, but Barbara convinces her that Slim is a very good "catch." To open Barbara's eyes to the hazards of married life, Bebe arranges to invite Mr. & Mrs. Wimple to a dinner at which they are to stage a fight. That evening, when Aggie answers the door, Slim, replete with costume, guns and guitar, rides in on his horse, Lupin. Ben finally opens the letter and discovers that that day is to be their last in the house. He and Bebe then decide to use reverse psychology and actually encourage the marriage. A chaotic evening ensues, highlighted by the arrival of a fire-eating Indian chief from Slim's show as well as Violet, who is crazy about Slim and wants to meet him. The Wimples start their fight and soon everyone is fighting with one another. Ben and Slim almost come to blows and Barbara breaks up with Slim. Hemmingway then arrives and tells Ben that he has changed his mind and signed the lease as he likes families and approves of Violet's interest in Richard. Richard however, is let off the hook when Violet and Slim are discovered kissing and announce their engagement, and all ends well for the Lyons.