Movie stuntman Tim Burke [John Lund] is hired by Denno Noonan [Barry Fitzgerald], the “social secretary” for Schuyler Tatlock, a wealthy but mentally fragile heir whose fortune has drawn the greed of relatives. Schuyler’s kin shipped him off to Hawaii to keep him out of sight, and Noonan has enjoyed a comfortable monthly paycheck watching over him. Two years earlier, Noonan had a drunken lapse and returned to find that Schuyler, after striking matches, had started a fire and burned to a crisp. He never notified the family, savoring the steady income instead. Then a telegram arrives ordering the return of Schuyler for the reading of the grandparents’ will, and Noonan hires Tim to impersonate the missing heir.
Tim dyes his hair and mimics Schuyler’s voice and mannerisms as best he can, and the deception quickly seems complete. Practically the entire family is fooled, including Nan Tatlock [Wanda Hendrix], the one relative who seems genuinely glad to see him. The greed-driven trio of relatives—Miles Tatlock [Monty Woolley], Gifford Tatlock [Dan Tobin], and Cassie Van Alen [Ilka Chase]—begins plotting to name themselves Schuyler’s trustees. They concoct a deal: Nan would receive a $100,000 annual allowance, with Cassie controlling the purse. Cassie also pushes for Nan to wed her own son, Nickey Van Alen [Robert Stack], to keep the fortune in the family. Tim overhears every detail of the scheme.
At his mother’s urging, the playboy Nickey starts courting Nan, and Tim’s growing jealousy fuels his interference. Cassie responds by having Tim locked in his room, but he escapes through a broken greenhouse roof and is knocked unconscious. When he comes to, he speaks with surprising lucidity in Nan’s and Nickey’s presence. Nan recalls that Schuyler’s irrationalities were once linked to a childhood head injury and hopes a second blow might have cured him; Dr. Mason [Leif Erickson] confirms that such a possibility cannot be dismissed, and Tim resolves to remain coherent.
Tim’s feelings for Nan deepen, and she returns his affection with a kiss that tests the line between brotherly and romantic love. But Cassie uncovers the truth and insists Tim preserve the impersonation, lest the entire inheritance go to a charity. After two years, Nan would come of age and Schuyler could be declared dead, allowing Cassie to protect the family’s wealth. Noonan explains to Nan that Schuyler had lucid moments before, only to relapse, and the two set off for Hawaii with the deception still in place.
Everything shifts when the real Schuyler emerges—alive and married to a Hawaiian woman named Kamamamalua. He is eventually tracked down by authorities after a string of arsons. In the end, Nan and Tim are finally reunited, and the tangled scheme collapses around them.
Along the way, a couple of notable cameos appear: Ray Milland as himself and Mitchell Leisen as himself, adding a touch of Hollywood legend to the family drama. The story also threads in Cora [Elizabeth Patterson] and Emily Tatlock [Dorothy Stickney], anchoring the clan’s older generation as the intrigue unfolds.
