A driver picks up a young seductive hitch-hiker. He takes her back to his place, and while he lies in bed, she stabs him.
Inspector Clifford arrives to investigate the gruesome case. The crime happens to be a carbon-copy of a previous murder with the heart of the victim being cut out by a billhook or a curved cutting tool. The investigating officers are not sure whether a woman could be responsible for such a crime.
While getting ready for work one morning, inspector Clifford overhears a breakfast show on the radio. Authoress Natalie Bell is discussing her book about a crazy Countess who cut out her lovers' hearts. Inspector Clifford telephones the breakfast show to find where he can contact Natalie Bell.
He speaks to Natalie and explains that no details of the murders have been released, but the method is the same as that in her book. She relates that the Countess lived three hundred years ago and has one surviving descendant, Mrs Henska, whom she has traced. Natalie proposes that she take the inspector to see Mrs Henska.
Mrs Henska relates the story of her ancestor. She tells how the Countess had numerous lovers who all ended up deceased. When her husband locked her up, the eagle that the Countess kept, tore out his heart.
As the number of the victims increase, the police keep their eyes on Tader, Mrs Henska's nephew, who happens to be a female impersonator. When Tader is proven to be innocent, inspector Clifford's suspicions turn on to Natalie.
Inspector Clifford and Natalie become close, but the inspector has to do his job and has Natalie's home searched. The search proves fruitless...
Natalie and Clifford get their relationship back on track after their brief difficulty and they spend a romantic evening together. At the end of the evening Natalie once more transform into the Countess and Clifford is dispatched.
Natalie finally lays the Countess to rest and moves on to research another murderess.