On a rainy London night in 1946, novelist Maurice Bendrix has a chance meeting with Henry Miles, husband of his ex-mistress Sarah, who abruptly ended their affair two years before. Bendrix's obsession with Sarah is rekindled; he succumbs to his own jealousy and arranges to have her followed. As the investigation progresses, we learn the reason for their separation. During a bombing raid, Sarah struck a bargain with God to sacrifice their relationship-in exchange for Bendrix's life. When Bendrix reappears in her life, Sarah realizes that her promise to God has become impossible for her to keep. She is placed in a spiritual dilemma as she struggles with her continuing love for her former lover in the face of the realization that she is fatally ill.