A New York businessman's dream of a country home is shattered when he buys a tumbledown rural shack.

One morning, like every morning, Jim Blandings, a $15,000-a-year advertising executive, wakes in his cramped Manhattan apartment and is forced to compete with his wife Muriel and their two children, Joan and Betsy, for bathroom privileges and closet space. Jim then learns from his best friend, lawyer Bill Cole, that Muriel has been talking to an interior decorator, who wants $7,000 to remodel the apartment. After vetoing the remodeling scheme, Jim goes to work, where he notices an ad for Connecticut real estate and decides suddenly that the family should move there. Soon after, an unscrupulous real estate agent named Smith convinces the trusting couple to buy a rundown Connecticut farm for $10,000. Later, Bill, who has discovered that the Blandings have not only been overcharged for the land, but have been hoodwinked about the farm's actual size, advises Jim and Muriel to re-negotiate the deal. Unwilling to jeopardize his idealized purchase, Jim refuses to file a complaint, but takes Bill's suggestion to consult a structural expert before renovating the dilapidated farmhouse. When Bill's expert declares that the house should be torn down, Jim and Muriel seek several "second" opinions and eventually hire architect Henry L. Simms, who convinces them to build a new house. Simms's modest plans for a new house are immediately expanded by Jim and Muriel, who demand one bathroom and two closets for each family member, as well as various hobby rooms. After the old house has been destroyed, Jim and Muriel learn that, because they failed to ask the holder of their mortgage for permission to tear down the property, they now owe him $6,000, the amount outstanding on their original loan. Although dubious about the entire deal, Bill offers to help Jim arrange to use his insurance policy as collateral for the construction loan. Soon after, however, Simms informs the couple that their additions will add $11,000 to the cost of construction. Shocked by the revised estimates, Jim and Muriel are about to terminate the deal when they see Simms's sketch for their dream house and are lovestruck by it. As soon as work gets underway on the house, unforeseen construction problems and questionable workmen begin to plague the Blandings. An imbedded stone "ledge" requires blasting before the foundation can be laid, and the water well cannot be built until costly drilling reveals a water source. Jim's work, meanwhile, is suffering because of his domestic distractions, and he is told by Bill, the firm's lawyer, that unless he comes up with a winning ad campaign for Wham ham in six months, his boss will fire him. Although confident his creativity will return, Jim is distressed to learn that, while an underground spring has been found, it is located under the house's proposed foundation and will have to be drained. Finally, following weeks of setbacks, the house's foundation is laid and building begins. Before the house is completed, however, the Blandings are evicted from their apartment. As soon as they move to their new home, Jim is informed that the window panes are the wrong size and that, in order to catch the early train to Manhattan, he must wake up at 5:30 every morning. Betsy and Joan then tell their harried father, who has felt increasingly jealous of Bill's close relationship with Muriel, that Bill's fraternity pin is in their mother's jewelry box and show him a diary entry from her college days in which she lovingly describes Bill. Jim later confronts Muriel with this "evidence," but she scoffs at his accusations and reassures him that she loves only him. A few months later, however, while Jim spends the night at the office trying to come up with his Wham slogan, Bill is stranded in rainy Connecticut and ends up staying the night alone with Muriel. Though still without his winning slogan, Jim decides to return home, fully aware that his departure will cost him his job. At home, after being told by Simms that a seemingly innocuous building request by Muriel has resulted in an additional $1,200 charge, Jim sees Bill dressed in his pajamas. Although Bill and Muriel maintain their innocence, Jim is furious and declares that he hates the house and wants to sell it. Before Jim's tirade concludes, however, one of the workmen interrupts to confess that he overcharged the Blandings $12.36 for his work and offers them a refund. Bill then tells the suddenly shamed Jim that, despite his criticisms, he truly loves the house and acknowledges that some things in life must be bought with the heart, not the head. Now convinced to stay in the house with his faithful wife, Jim is further relieved when Gussie, the maid, utters the phrase "If you ain't eatin' Wham, you ain't eatin' ham" while serving breakfast. Jim turns the phrase into his job-saving slogan, and sometime later, he, Muriel, Joan, Betsy and Gussie enjoy their beautiful dream house with their dear friend Bill.