In 1918, a World War was raging and a lethal strain of influenza was circling the globe. In the midst of all this death, a bizarre disease appeared in Europe. Eventually known as encephalitis lethargica, or sleeping sickness, it would spread across the world, leaving millions dead or locked in institutions. Asleep, set in 1920s and 1930s New York, follows a group of neurologists through hospitals and insane asylums as they try to solve the mystery behind this worldwide epidemic.