I woke up in the middle of the night—my husband wasn’t in bed. The digital clock on the nightstand pulsed a rhythmic, bleeding red: 3:12 a.m. I lay there for a moment, waiting for the sound of the shower or the flush of a toilet, but the house was tomb-silent. My skin prickled. Mark was a heavy sleeper, the kind of man who drifted off during movie credits and didn’t stir until the coffee pot hissed at 7:00 a.m. I rolled over and felt his side of the mattress. It was cool. He had been gone for a while.