Watch 'Deadly dreams' this Friday on Dateline

A case that hinges on the mysteries of the mind, and the science of sleep. We know people can talk in their sleep, walk in their sleep, even drive – all without realizing what they're doing, or remembering it afterwards. But is it possible to kill while unconscious? DATELINE Correspondent Keith Morrison reports on what happened during one couple's weekend getaway in the dead of night.

Watch "Deadly Dreams" Friday night at 10 p.m. ET, 9 p.m. CT on NBC.