Time-travel movies are, and always will be, the ultimate in mind-bending entertainment. Whether it's something as frivolous as the Back to the Future trilogy, as action-packed as The Terminator series or as baffling as Donnie Darko, the time-travel plot device introduces paradoxes that are nearly impossible to wrap your head around, let alone concoct into a believable story.

Now entering that fray is Looper, which has a truly high-concept premise. Joseph Gordon-Levitt plays Joe, a so-called looper whose job it is to kill people sent to him from the future by groups like the Mob, who are unable to accomplish that task in their time. How he got involved in this pursuit and why he accepts it on what seems to be blind faith is never really addressed; it just is. But the tidy arrangement threatens to get blown to hell when the 30-years-older version of himself (Bruce Willis) is sent back for him to kill, only to escape when he hesitates just a moment too long.

The twists and turns in Looper deserve to be experienced with no further description, but suffice it to say that the cat-and-mouse game between young Joe and old Joe is both thrilling and emotional. It involves a present-day crime boss (Jeff Daniels) and his bumbling underlings; two beautiful women (Piper Perabo and Emily Blunt), whose interactions with both versions of Joe are key elements; and a young child whose future self sets into motion almost every event in the movie.

Writer/director Rian Johnson has been making a name for himself among serious moviegoers since 2005. His unique take on the private-eye genre with Brick (also starring Gordon-Levitt) was an audacious debut, and 2008’s The Brothers Bloom, while not quite as successful, found him inching a bit more toward the mainstream both in terms of the actors and the plot, which involved con men out to dupe an heiress.

Looper brings together the best of both worlds, putting out a voice that is distinctly Johnson’s while also making the story accessible enough to mainstream audiences that they can appreciate its nuances. The time-travel aspect is dealt with smartly, addressed just enough to make it integral to the film but not so much that it gets bogged down in details. Johnson even takes this head-on in a couple of scenes, having characters dismiss time-travel minutiae as unimportant.

And that’s what makes Looper so great. The central premise draws you in, but what keeps you watching is the way Johnson teases out various relationships, especially the one between new Joe and old Joe. Gordon-Levitt and Willis play off each other in fantastic ways, with Gordon-Levitt’s subtle facial prosthetics completely selling that he’s Willis’ younger self. The supporting cast acquit themselves well, especially Daniels and Blunt.

Looper is the type of movie I was waiting all summer for, one that exudes terrific action, intelligence and heart at the same time. If this is the signal for the start of fall movie season, we’re in for a great end to 2012.