It's 2027 London, and everything is in disarray. Immigrants are being rounded up into detention camps, and due to unexplained fertility issues, no new people have been born anywhere on Earth for the past eighteen years. Thus, humans will become extinct in less than a century, a point that's led to chaos as well as people like Theodore Faron (CLIVE OWEN) seeing nothing but a pointless, bleak future. While he enjoys spending time with his reclusive, hippie friend Jasper Palmer (MICHAEL CAINE) who lives out in the woods, Theo can't get past all of the gloom and doom, unlike his live-in-the-moment cousin Nigel (DANNY HUSTON).
Things change, however, when rebel forces known as the Fishes kidnap and deliver him to their leader, Julian Taylor (JULIANNE MOORE). She's his former wife who fights for equal rights for all people, and hopes he can get transport papers for an illegal immigrant, Kee (CLAIRE-HOPE ASHITEY), and her traveling companion Miriam (PAM FERRIS).
Theo agrees for the pay, but then discovers the underlying cause of Julian's urgency -- Kee is pregnant. Realizing the ramifications of her state, Theo, along with Fish such as Luke (CHIWETEL EJIOFOR) and Patric (CHARLIE HUNNAM), then set out hoping to deliver her to a sort of seaside sanctuary known as "The Human Project."
Along the way, Theo and Kee must deal with treachery from within their own ranks, various questionable outsiders such as Syd (PETER MULLAN), as well as traveling through a full-blown war zone where government and rebel forces are engaged in battle, unaware of what's in their midst and lies in the balance of their actions.