Everyone remembers exactly where they were, the day the ships came.

What no one knew back then, though, was that there were people who were already expecting them.

Scottish psychologist Elspeth McGann thinks her patient Lester Rains—a suave, enigmatic man who claims to be have been alive for 2,000 years and to be part of a team of extraterrestrial 'farmers' waiting on Earth for an alien harvest—is a delusional schizophrenic. But when vast ships suddenly appear over Moscow and vacuum up 50,000 people in a matter of hours, she realizes she must track down the elusive Rains. In her search, she stumbles upon a group who are already trying to track down the farmers. This band of renegades is led by Cassius C. Trenton, a former NSA analyst who has been on the run since he broke the code on a mystery transmission beamed into space from Earth years ago, and which bore a single, chilling message: Ripe.

With the aliens set to return, and some world leaders complicit in their plans, Elspeth and Trenton must seek out Rains and find a way of escaping the impending apocalypse, a hunt that takes them from Edinburgh to the White House, only to discover the harvest is just the beginning.