Apparently the disappearances began in 1946, but suddenly on the heels of an incoming comet, 4400 individuals who had mysteriously vanished during the past 60 years, appear with no memory of where they'd been, who took them, and what they'd been doing. Oh yeah, they also haven't aged. The pilot episode follows four of this group as they make the difficult transition back into a world that for some now holds little meaning. Airing on the USA Network between 2004-2007, the series ran for 44 episodes spread over four seasons.