Patricia Highsmith has her own chilling interpretation of the suspense thriller genre. You wonder not so much about what will happen or how it will happen or who will do it. Rather, the question is: how much worse can things get for the relatively innocent main character, Robert Forrester, who, as the novel goes on, is falsely suspected of a growing number of deaths.
Forrester invites suspicion by prowling around the house of a young woman. Depressed by the failure of his marraige, he has moved to a small Pennsylvannia town and is leading a solitary and bleak life. Looking through the windows of Jenny's house, he is comforted by watching the attractive young woman attend to domestic details: cooking, hanging curtains, talking to her boyfriend over dinner.
Highsmith presents Forrester's prowling as understandable; slightly wrong, and risky, yet certainly not harmful. Mostly one feels sympathy for Forrester, a character drawn in anguished shades of gray. He is a decent man, with no drive or hope, seeking a little illicit happiness.
As the novel progresses, his relationship to Jenny takes a surprising turn of events. Highsmith's mastery lies in the pedestrian inevitability with which she introduces abnormal and even shocking twists of the plot. Because we are lulled into Highsmith's own distinctive world of the darkness of ordinary lives, our anxiety for Forrester is gradually heightened without our even being aware of it. By the time the plot gets around to the events which categorize the novel as a mystery, we are deeply engaged in the psychologies of Forrester and Jenny, as well as several other characters.
The suspense thus springs from their own interior struggles, rather than the machinations of a conventional murder plot. Predictably, therefore, there are no easy solutions in the end, no complex train of events to be tied up in one simple explanation.
The adding up of the actions of people who are no more conscious of why they do what they do than any regular person, has, in this novel, an utterly gripping and painfully believable tragic outcome.