Ruth, Kathy and Tommy are three children at what seems to be a special boarding school in England. The kids are taught how to behave and that if they leave the school grounds something terrible will happen to them. They are best friends until they become teenagers. Ruth (Kiera Knightley) is jealous of the obvious chemistry between Kathy and Tommy, so she becomes his girlfriend. Kathy doesn't fight for him. In fact, everyone, including all the other students, are a bit too passive. We learn that this is a different world from our Earth. While many things are similar it's revealed that mankind has embraced using clones to extend human life--and that this trio are being raised as organ donors. When Kathy and Tommy reunite as adults, Kathy is a caregiver for the donors and Tommy has gone through his second surgery. They think that if they can prove they are in love that they'll be granted more time together.
Although this is primarily a love story, it's a creepy, unsettling movie. Granted, it's not as blatant as THE CLONUS HORROR but it deals with the subject in a realistic way.