Once, years ago, I found myself in an ice-cold bath with no memory of walking to the bathroom or running the tub. Another time, I terrified my friend by leaving our hotel room in the middle of the night—then pounding on the door, demanding to be let back inside. Both times, I awoke in the middle of these bizarre incidents. I had been sleepwalking—but I never knew why until I researched the strange phenomenon for my latest story.