1.1 - The world is thrown into turmoil when a comet is discovered to be on a collision course with Earth, but instead of smashing into the ground the ‘comet' explodes in a ball of light leaving behind thousands of people. These are the 4400, a group of missing persons who had disappeared over the previous 60 years from all over the world. None of them have aged a day and no-one can remember anything about where they have been or what happened to them. The American contingent are sent into quarantine where two Homeland Security agents, Tom Baldwin and Diana Skouris, are assigned to investigate. An assignment that is especially pertinent to Baldwin because his nephew, Shawn, is one of them, and it's not long before some of the 4400 begin showing signs of strange, preternatural abilities that prove too difficult to control for one of the returnees - with fatal results. Elsewhere, love is blossoming for two of the 4400 as Lily and Richard find solace in each other when it is clear that life back home has moved on without them.