The future, 2044. Time travel has been illegal since its invention. Only when the gang wants to clean up a specific target and does not want to leave any traces in this world, will the "loop messengers" be dispatched. They are responsible for executing those who are teleported back to the other world by time. They are called "loop messengers" because they must eventually kill their future selves - so as not to leave any trouble for future customers. This process is called "sealing the ring". Killer Joe (Joseph Gordon-Levitt) is the youngest loop messenger, with a perfect shot, but when he wants to execute his future self (Bruce Willis), he is fiercely resisted and fails. Old Joe hopes to kill the key figure in the future ring-sealing plan-the rainmaker, so as to change the fate of his wife (Xu Qing); young Joe meets Sarah (Emily Blunt), a single mother on the farm, in the process of chasing and killing, and unexpectedly becomes the protector of a mother and son. The two versions of Joe each come up with their own unique strategies in this gamble to change the future (and the present), staging a peak confrontation of their egos...