Time-travel stories are by definition ridiculous, and one could easily describe “Looper” as—well, loopy. But writer-director Rian Johnson, following up his audacious if uneven debut, the 2006 high-school noir “Brick,” acknowledges the fact in a bit of dialogue, in which Joe (Bruce Willis), asked by his younger self (Joseph Gordon-Levitt, decked out in jaw makeup to give him a vaguely Willisian look) to discuss the ramifications of the process, dismisses the question by saying it’s too complicated and confusing to get into. The gag tells you Johnson’s in on the joke.

And if you’re going to make a time-travel-movie, it’s wise to take as your model—as Johnson obviously has—one of the best, “The Terminator.” The indebtedness is obvious, but the script cleverly manipulates the material to give it a spin all its own. The result is faintly absurd, but done up with such confidence that you’re willing to go along for the ride.

The set-up has Gordon-Levitt a futuristic hired killer called a looper. He’s part of a gang of young gun-men in a dystopian city working for the city boss (Jeff Daniels, giving a smoothly bemused performance) who’s actually a crook from the future overseeing the loopers’ work. Their job involves dispatching people sent from the future, trussed up with bags over their heads, with a single rifle blast and then disposing of the bodies. The procedure is necessary because in the earth where the victims originated, it’s almost impossible to get rid of a corpse without being found out. But there’s one hitch in the process: eventually a looper will be required to kill his future self in what is called “closing the loop.” He’s then provided with plenty of dough and allowed to live out his prescribed thirty years or so in comfortable retirement—until, of course, he taken prisoner and sent back for execution by his younger self.

Occasionally, though, the system goes awry. That happens in the case of the solitary Joe’s only semi-friend, Seth (Paul Dano), who, when confronted by his future self as his latest victim, freezes and lets him escape. The way in which the mob handles the situation involves torturing the “present” Seth until the older one surrenders—something shown in macabre detail. And Joe, whom Seth had tearfully asked for help, ultimately abandons him in his own self-interest.

Of course the case is different when Joe finds himself in the same predicament. After his future self (Willis), a particularly canny fellow who’s readied himself for the inevitable, escapes in the “present,” Joe goes on the lam before the mob can capture him, intending to resolve the matter by tracking down and killing future Joe himself. The matter’s complicated by the fact that Old Joe saw his wife, who redeemed him from his shabby existence, killed during his capture, and is out to alter that tragedy by finding, and offing, the brutal future boss, called the Rainmaker, who’s killing off all former loopers. That fellow is a mere child in the “present,” and Joe finds himself protecting the kid (Pierce Gagon) and his mother (Emily Blunt) from his future self, becoming emotionally attached to them in the process.

The script has been festooned by Johnson with all sorts of other business, like the ambition of one of the boss’s enforcers, Kid Blue (Noah Segan), to take care of the two Joes on his own, and showing up at the most inopportune times; the determination of Old Joe to end the Rainmaker’s rule before it begins, despite the fact that he doesn’t know too much about the youngster’s identity; and the fact that a percentage of the “present” population are mutants, endowed with various degrees of psychokinetic power. And of course one also has to deal with that old bugaboo of time travel—the inconvenient fact that any alteration in the present can change the future in significant ways.

Johnson works his way through all the contortions with aplomb, working with cinematographer Steve Yedlin to give the film visual fizz and editor Bill Ducsay to keep it moving fast enough to conceal logical lapses, while using narration and flash-forwards intelligently to keep us up to speed on the “rules” he’s established for the game. And if Gordon-Levitt still seems rather thin and boyish for an action hero, with help from stuntmen and a stellar visual effects crew he gets the moves right, and certainly projects the vulnerability his character needs. Willis is pretty much just Willis, but like John Wayne before him, that’s enough; and he’s certainly not afraid to show Old Joe’s ruthlessness. Blunt is fine as young Joe’s potential romantic interest, and Gagnon puts across the various layers of the Rainmaker-to-be exceptionally well, testimony not only to his abilities but Johnson’s directorial skill. Bridges seems to be having a good old time with the villain’s role, and Dano makes an indelible impression in a relatively small part.

Excellent craft contributions across the board (production designer Ed Verreaux, art directors James Gelarden and Scott Plauche, set decorator Katherine Verreaux), as well as by the large effects team, add to the success of what might have been a too-hard-to-swallow tale, and Nathan Johnson’s background music scores as well.

The result is a wild trip that—like the original “Terminator” and “Matrix” films—is well worth signing on for.