The Looper business model. You're young and your prospects are limited. Working as a looper is high-paying, easy work in a Crapsack World. There's a catch but it's so far away you don't even care. Then one day your paycheck is a different color and it means there's a very special person under that bag on their head. You can take your money and run as far as you can but you know that in exactly thirty years, somehow,that person is you.
CID. He's a Creepy Child with a bad temper and telekinetic powers. He killed the aunt that raised him, and his mother has to hide in a safe when he has a tantrum. In the future, he ends up becoming a crazy mob boss who wants revenge on the loopers. How he does this is unknown, but it's safe to say it's not pretty. Worst of all, it's not certain this future has been prevented at the end of the film.
Old Seth literally falling apart as Young Seth is being mutilated alive.
Probably one of the most nighmarish scenes out there in the eyes of many. Just check the comments.
Specifically, the scene where he's trying desperately to get to the place he knows they're going to kill him, but they aren't stopping at any point. One of his legs disappears while he's in the car, making him crash outside. As he hobbles towards the door, his other leg vanishes. By the time he's beating on the door begging them to stop in a tongueless moan, he's nothing but a head, torso, and set of stumps. Then the doors swing open ominously, and Kid Blue steps out and shoots dead what's left of Old Seth. As he drags the remains inside, we see the mutilated Young Seth lying on an operating table, and hooked up to a ventilator.
All of this is granted another layer of horror when Old Joe mentions, later, that he gains the memories of his changing past as it happens. Which means Old Seth would be remembering exactly what was being done to him, in real time.
One particular moment that you'd most likely miss on first viewing? After Old Seth decides to ignore the message being scarred onto his arm, he starts climbing a chain-link fence. Within a split second as he pulls himself up, his right pinkie finger vanishes. An instant later, his ring finger is gone. Then his middle finger, and his nose, and several teeth.
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