A playboy squanders his wealth and must seek out a new source to maintain his idle rich lifestyle, namely marrying a rich woman and ... murdering her.

After picking up his cherished but worn out Ferrari sports car from the mechanic shop, self-absorbed playboy Henry Graham spend the next several days avoiding his attorney, Beckett. Discovering that several of his checks to his private club have bounced, Henry suspects Beckett is trying to lure him to his office and reluctantly goes to see him. At the lawyer's office, Henry learns that he has squandered his entire fortune and is dead broke. Shocked and traumatized, Henry spends the next several hours wandering through his favorite stores and clubs bidding them farewell. At his lavish apartment, Henry considers his priceless collection of first edition books and rare modern paintings, then asks his trusted manservant Harold what he would do if he learned Henry had no money. Harold admits he would give notice immediately. After experiencing horrifying visions of the common life, Henry confesses to Harold and sadly admits the only real talent he has is being rich. Harold suggests that Henry consider "taking the plunge" by finding a suitable, extremely wealthy woman to marry, then gives notice. Weighing this option against suicide, Henry agrees to try to find a wife and turns to his stingy Uncle Harry for help. Henry proposes that Harry lend him fifty thousand dollars, which he vows to repay in six weeks after getting his affairs in order and finding an affluent wife. Dismayed when Harry agrees with the single stipulation that should Henry fail to repay him in time, he will then owe him ten times the borrowed amount, Henry nevertheless agrees. Over the next five weeks, Henry avails himself of any and all wealthy female company, only to be consistently mortified by their demands on him. Despondent as the final week looms with no marriageable contender in sight, Henry is buoyed by steady encouragement from Harold, who has remained with Henry during his desperate quest. At a small society party, Henry learns from his friend Bo that one guest, the solitary, drab and clumsy woman there, is the exorbitantly wealthy heiress Henrietta Lowell, a botanist deeply involved in research and writing. Delighted, Henry introduces himself to the shy Henrietta, who drops her tea cup twice, infuriating the hostess. Henry escorts Henrietta from the party and offers to drive her home. When Henry's Ferrari breaks down, the couple spends all night in the car waiting for a tow truck, and Henrietta admits her greatest wish is to discover a new species of fern never before classified. Henry asks the overwhelmed Henrietta on a date for that evening then hastens to his apartment to familiarize himself with botany. At dinner that evening, Henrietta is mesmerized by Henry's knowledge and sophistication, but revolts him when she reveals she has always fancied Malaga Coolers made with Mogan David extra heavy Malaga wine. The next evening, despite Henrietta spilling Malaga wine on Henry's llama rug, Henry proposes and the smitten Henrietta accepts. Later at home, Henry confides in Harold his feeling that Henrietta's appalling taste makes her a menace to society who does not deserve to live, but forges ahead with immediate plans to wed. When Uncle Harry reads the wedding announcement in the next day's paper, he contacts Beckett, who provides information about Henrietta's attorney, Andrew McPherson. That afternoon when Henrietta stops at McPherson's office, he begs her not to marry Henry, but she remains firm. Later, McPherson summons Henrietta and Henry to a meeting, where he reveals that Harry has provided him with a copy of Henry's loan agreement, which proves he is a penniless gold digger. Henry admits to arranging the loan, but insists it was to clear his debts before committing suicide. He then explains that meeting Henrietta changed his mind. Despite McPherson's pleas, Henrietta insists on making Henry a joint co-signer on all her bank accounts and demands that the loan to Harry be paid before the wedding the next day. After the wedding, on their island honeymoon, Henrietta investigates the native plant life while Henry studies various toxicology books with the intention of poisoning his new wife. Henrietta finds a fern she does not recognize and upon returning home, submits it to the university. At Henrietta's enormous estate, Harold greets Henry with a warning that the servants, led by coy housekeeper Mrs. Traggert, are unmanageable. After Harold finds the household budgets books under Mrs. Traggert's mattress, Henry goes over them carefully and discovers the staff has been heavily padding the accounts which are supervised by McPherson. With Henrietta's consent, Henry fires the servants and terminates McPherson's authority, assuming management of all Henrietta's financial affairs. After Henry learns from the gardener that there are no chemicals on the grounds because Henrietta supports organic materials, he renews his attempt to obtain poisons. When Henrietta invites him to accompany her on her annual field trip to the Adirondack mountains, Henry imagines her falling victim to wild natives or unruly animals and readily agrees. While packing Henry's revolver for the trip, Harold congratulates Henry on the success of his marriage, pointing out that he has displayed remarkable abilities in finance and management and that Henrietta trusts him completely. That afternoon Henrietta happily reveals the university has confirmed that her fern submission is a new species and that instead of following tradition and naming it after herself, she has named it "Alsophilia Grahami," using her new husband's name. When Henrietta presents Henry with a necklace containing a small piece of the newly named fern and thanks him for giving her confidence, he is uncomfortably touched. On the field trip, the mosquito-addled Henry takes no homicidal action against Henrietta, hoping some accident may occur. When their boat overturns in the river rapids, Henrietta clings to a log and tells the thrashing Henry she cannot swim. Assuring Henrietta he will save her, Henry reaches the shore, ecstatic that he can do away with his wife at last. Calling to Henrietta to let go of the log and let the current carry her to him, Henry turns away from the shore only to find himself surrounded by Alsophilia Grahami. Unexpectedly elated, Henry searches for his necklace and panics when he realizes that he has lost it in the river. Cursing as he realizes that despite all his plans, he has fallen in love with Henrietta, Henry rushes to the river's edge to save her after which they walk back together as Henrietta happily plans their future.