[1] Ramon, a devoutly Catholic furniture repairman in Mexico City meets Theo, a wealthy German atheist expatriate who questions the happiness he had found in his new home: "Theodore thought he was as happy as anyone logically could be in an age when atomic bombs and annihilation hung over everybody's head, though the world 'logically' troubled him in this context.

An unlikely friendship develops, until Lelia, a woman they have both slept with and care for, is found brutally raped, murdered and mutilated.

They learn that Lelia may have been robbed and track a suspect to Acapulco, but Theo believes he is under surveillance.

[2] Highsmith herself had a negative opinion of her novel, regretting her attempt to write in the mystery genre.

She later wrote: I had tried to do something different from what I had been doing, but this caused me to leave out certain elements that are vital for me: surprise, speed of action, stretching the reader's credulity, and above all the intimacy with the murderer himself.