I slept with my ex-wife again on a business trip, and at dawn, a red stain on the sheet left me breathless. A month later, a call from a hospital in Miami made me realize that that night hadn’t been a mistake—but rather the beginning of something much darker.

“It’s not what you’re thinking,” she said, with a quickness that made me feel even worse.

She held the sheet tightly in her hands, as if she could erase it with her fingers. I remained motionless, my heart hammering in my throat.

“Then explain it to me,” I blurted out.