The Woman in the Fifth, by Douglas Kennedy

Harry Ricks is a man who has lost everything.

A romantic mistake at the small American college where he used to teach has cost him his job and his marriage. And when the ensuing scandal threatens to completely destroy him, he flees to Paris.

He arrives in the French captial in the bleak midwinter, and ends up having to work as a night guard to make ends meet. Then Margit, a beautiful, mysterious stranger, walks into his life. But their passionate and intense relationship triggers a string of inexplicable events, and soon Harry finds himself in a nightmare from which there is no easy escape.