The End of the Affair (movie tie-in)

The novelist Maurice Bendrix's love affair with his friend's wife, Sarah, had begun in London during the Blitz. One day, inexplicably and without warning, Sarah had broken off the relationship. It seemed impossible that there could be a rival for her heart. Yet two years later, driven by obsessive jealousy and grief, Bendrix sends Pakris, a private detective, to follow Sarah and find out the truth.