If you have any interest at all in seeing Looper, you probably already know the premise. It's a time-travel story. Time travel is discovered and immediately made illegal, but in 2074 gangsters use it to dispose of people they want to get rid of. The victims are cuffed, hooded, and sent to a spot in Kansas outside a cane field. Their executioners, known as Loopers, are waiting for them. The victims appear, get shot, and get disposed of. One of the Loopers, Joe, played by Joseph Gordon-Levitt, finds himself facing his own future self, played by Bruce Willis, who's missing the hood and cuffs. Willis avoids the killing shot, flattens Gordon Levitt, and escapes.
It seems that 2074 isn't a happy place (not that 2044 is, either). A boss called The Rainmaker is sending all the old Loopers back to die, and while capturing Bruce, the men sent to get him have killed his wife. So Bruce is going to kill The Rainmaker in 2044 to save his wife's life. Time-travel paradoxes? That's just the beginning. That's also all I'm going to say about the plot. The screenplay has some nice surprises, and it's best to let the movie spring them on you.
Gordon-Levitt has a good time playing a young Bruce Willis, and Willis has a good time playing an old Gordon-Levitt. Emily Blunt shows up for a nice turn, and there's a kid actor named Pierce Gagnon, who's really good. Jeff Daniels is great as the crime boss in 2044. If you like good SF movies or action movies or just plain good movies, give this one a try.