Nick Charles [William Powell] visits his wife Nora Charles [Myrna Loy] in Sycamore Springs, Nick’s hometown in New England, where the locals are convinced he’s in town on an actual investigation, even as he quietly denies any case is on his radar. The town’s skepticism quickly spirals into a web of rumor and suspicion, turning a peaceful weekend into a stage for whispered theories and curious glances.
The tension spikes when Peter Berton [Ralph Brooke], an employee at a nearby aircraft factory, is shot dead before he can reveal what he knows. An old childhood friend, Dr. Bruce Clayworth [Lloyd Corrigan], steps in to perform the autopsy and pulls a pistol bullet from Berton’s body, a clue that hints at a more intricate plot than a simple crime of passion. As Nick begins to rummage through Berton’s room for leads, he is suddenly knocked unconscious by Crazy Mary [Anne Revere], a local eccentric whose odd behavior complicates the mounting questions.
A seemingly ordinary birthday gift—Nora’s purchase of a painting for Nick—becomes the linchpin of the mystery. When she shows the artwork to Nick, it dredges up painful memories and prompts her to donate it to a charity bazaar. Edgar Draque [Leon Ames], a suave but wary figure, tries to wrest the painting away by offering Nora a large sum, while his wife Helena Draque [Helen Vinson] publicly claims ownership. The painting disappears after Helena is knocked out, and it is finally discovered by the Charles family dog, Asta, in Crazy Mary’s shack, turning a quiet artifact into a dangerous clue.
With time running short, Nick calls all suspects to his father’s house, a setting that brings together generations and grudges alike. Dr. Bertram Charles [Harry Davenport], Nick’s stern father, has never fully supported his son’s unconventional career, but he becomes a pivotal ally as the case unfolds. Using the fluoroscope, a device trusted by the family, Nick reveals a hidden blueprint beneath the painting—an item of immense value to a foreign power because it contains specifications for a new aircraft propeller. Berton had copied the blueprints and concealed the copies behind five paintings, a detail that explains why so many people are entangled in the scheme.
As the plot thickens, Berton’s murder is tied to a broader spy operation, and the Draques are revealed to be part of the ring. The mastermind behind it all is Dr. Bruce Clayworth, whose earlier action—presenting a supposed weapon’s evidence—betrays his deeper plan. Nick deduces the truth by examining the murder weapon’s trajectory, noting that the real bullet would not have penetrated Berton’s body as far as it did. The claim hinges on a World War II Japanese Nambu sniper rifle belonging to Dr. Clayworth’s brother, brought in as a prop in the investigation, which Nick uses to unsettle the killer.
Clayworth makes a final, desperate move to shoot Nick, only to discover that the firing pin has been removed—a safeguard Nick anticipated. With the weapon rendered useless, the tension breaks as the spy ring’s leadership falls into the open, and Dr. Clayworth’s motive—rooted in childhood rivalry and jealousy—becomes clear. The case closes with a sense of resolve and pride, as Nick’s father reflects on his son’s tenacity, and the town begins to see that, beneath the charming surface of the Charles family, a discreet, relentless detective work thrives.
