"A major defining factor was my wanting him to be part of the DC Universe. Because if someone as powerful as the Sandman was running all the dreams in the world, a natural question would be "Why haven't we heard about him by now?" The answer I came up with was "He's been locked away." And that solution formed an image in my head of a naked man in a glass cell. My next question was "How long had he been trapped there?" The movie hadn't been made yet, but I'd read Oliver Sacks's book a few months earlier, so I knew about the encephalitis lethargica, or "sleepy sickness," that had swept Europe in 1916. Scientists to this day don't understand what caused it, and I loved the idea of blaming it on the Sandman's imprisonment, so I determined the length of his stay to be seventy-two years--ending in late 1988, when the series debuted. And so on; each plot point just seemed to naturally lead to the next one."