The taillights of Dave’s sedan glowed like malevolent red eyes in the deepening twilight. Annie’s knuckles were bone-white on the steering wheel, her heart hammering a frantic rhythm against her ribs. For weeks these secret outings with his father, Roger, had frayed her nerves to the breaking point. The vague answers, the whispered phone calls, the faint unfamiliar scent that sometimes clung to his collar—all of it had coiled into a tight knot of suspicion in her gut. Tonight she had to know.

She followed them downtown into a district of anonymous grey-brick buildings. Dave’s car slid into a parking spot and the two men—so alike in their confident stride—disappeared...