Joseph Jones, the leader of Silver Haven, a phony Long Island cult, is informed by his lawyer, Jennings, that although one of his deceased followers has left a one million dollar estate to him, the interest will go to her nephew, Upshaw, until Upshaw's death. While Jones and his cohorts try to think of a way out of their dilemma, the butler, "Noose" Green, is listening to a radio broadcast of popular Wally Benton, who writes and performs murder mysteries in which his alter ego, "The Fox," solves seemingly perfect crimes. Jones's cohort, Beau Smith, gets the idea that Wally would be the perfect person to help them get rid of Upshaw. Meanwhile, Wally is about to elope with his longtime fiancée, Carol Lambert, but, because his contract is up for renewal, reluctantly agrees to his manager "Buzz" Baker's request that he go out once more with "Fran" Post, the sponsor's man-chasing daughter. That night, Jones and his men arrive at Wally's dressing-room, posing as manufacturers of a health tonic that rivals Post's, and promise to double his contract. They insist that he go with them and promise that both Carol and Fran will be notified that he has been detained. Wally soon realizes that Jones is not a sponsor and that he has been kidnapped. At Silver Haven, Jones informs Wally of his need for "the perfect crime" and coerces him to help by bringing the confused Fran and Carol to the estate. When the three are alone, they try to find a way out, but wind up in the same room as Jones after finding a secret passageway. Jones forces Wally to stay alone until he concocts the perfect murder as Upshaw will be flying to New York from Kansas City the next day. Meanwhile, Fran's father, Philip Post, has become worried and contacts Deputy Commissioner O'Neill, who thinks that Fran has eloped with Wally, much to Post's displeasure. The next morning, after Wally has successfully developed a perfect murder idea, he tries to bribe Noose with a radio contract to let them free, but Jones interrupts. Wally then happily explains his loophole-proof plan: the poison will be placed in Upshaw's tooth powder and after he gargles, all traces of the poison will disappear and the death will appear to be from heart failure. Jones is about to send his henchman, Gordon Thomas, to Kansas City to sneak the poison into Upshaw's toiletry case, but first tries out the powder on Noose, who immediately dies. Later, Wally secretly tells Fran and Carol that he substituted sugar for the poison, but when Thomas forgets Wally's packet, Jones's druggist, Herman, makes certain that Thomas receives a fresh poison packet. Some hours later, Upshaw boards his plane and Thomas sits across from him. At the same time, after fruitlessly trying to coerce or overwhelm their guard, Sylvester, Wally rigs a portable radio with a disconnected telephone wire and is able to contact a telephone operator, who signals Upshaw's plane. Because Thomas has tampered with the plane's communication system, Wally cannot warn Upshaw, but is able to have the operator connect him to his radio station and relate the facts as if they were part of his regular program. The radio staff and Mr. Post realize what is happening, as does Smith, who summons Jones to the estate. A child's radio eventually broadcasts the warning to Upshaw just as the police and Post arrive at Silver Haven. After the police arrest Jones and his gang, Wally finally speaks with Upshaw, who not only promises not to brush his teeth, but says he won't even take them out.