The Cry of the Owl by Patricia Highsmith

Anyone familiar with Patricia Highsmith's two most famous novels, Strangers on a Train and The Talented Mr. Ripley​, will recognize the premise of The Cry of the Owl: two men engage in mortal combat and the woman (or women) in the their lives don't seem to know what's happening.

The Cry of the Owl begins with Robert, recently divorced and moved from Manhattan to a small town in Pennsylvania, stopping along a road near a house to look through the kitchen window and watch Jenny washing dishes and doing other chores. 

I won't give away the plot developments that lead to Robert's conflict with Greg, who has been dating Jenny. I will say that what could play out as a conventional romantic triangle turns into something more ambiguous. Each of the relationships---Robert-Jenny, Jenny-Greg, and Robert-Greg---is strange yet plausible, just as they are in Highsmith's more famous novels.

The ambiguity of the relationships no doubt stems from Highsmith's situation. She was gay, and she published most of her work in the 1950s and 1960s. Although she wrote one novel about a lesbian relationship (The Price of Salt, 1952), for most of her career she wrote about relationships between men and women. But she let her truth shine through them.