Life is good for Ann Hamilton (Katharine Hepburn), living with her popular scientist father and poised to become a spinster scientist herself, until one fateful night she meets the inventor Alan Garroway (Robert Taylor) whose distance controller has revolutionized the aeronautics industry. Alan woos Ann and they marry in a whirlwind affair with Alan whisking Ann away to Washington to live. In Washington Ann realizes that she knows little of Alans past, particularly his emotionally charged relationship to his brother Michael (Robert Mitchum), rumored to have bankrupted the company Alan and he had created. Michael is missing and has been absent for years with speculation by many that some dark activity may be connected to his disappearance. When people keep mentioning Michael to Ann she asks Alan and every time Alan responds with drama, at one point verbally abusing Ann for her interest in the brother. When Michael appears lat one night to confront Alan about how he obtained his original plans and patent for the long-distance regulator that has made him a millionaire, Alan plans a method of revenge that includes another murder.