A glowing ball of light travels to earth and then dissapears - leaving 4400 confused people standing on a lake shore. They are 'abductees', taken from their lives over the past fifty years, now deposited at exactly the same age as when they left. The government releases them into the community, but soon realises that something strange is going on - the 4400 have special powers - supposedly given to them by aliens. But is this really true? Who are the 4400? What is their purpose? Why have they been returned?
Two agents, Tom Baldwin (Joel Gretsch) and Diana Skouris (Australia's own Jacqueline McKenzie) try to answer these questions as they try to help these displaced people. Soon they realise that the 4400 are part of something much, much greater, an essential cog in a plan that transcends time itself, and will determine the fate of the earth.