One of the oldest time travel "what if" questions deals with the very idea of changing the future through one single action.  "If you could go back in time and kill Adolf Hitler as a child, would you?"  After all, with that one action, you would erase so much pain and horror that it seems like a more-than-fair trade, right?

But what if instead of immediately leaping to the idea of murdering a child, no matter who that child is or is going to become, you took a less easy route?  What if you went back in time and raised Hitler Jewish instead?  What if instead of killing him, you connected him to a faith and a tradition and you changed his entire set of values and beliefs?  It's not a single action, and it doesn't sound easy, but it does raise a far more pointed question about the hypothetical situation.  Can you erase an evil by committing an evil?  Can you do good by doing bad?

Rian Johnson's "Looper" is one of the year's best films, no doubt about it, and a huge jump forward for a filmmaker whose first two films both exhibited a strong, clear voice and a real sense of style and command over film language.  As much as I liked both "Brick" and "The Brothers Bloom," they are not films that are easy or simple to like.  Johnson is obviously incredibly bright, and as with many extremely smart people, he has a tendency towards the complicated, the dense.  His films so far have been rewarding, but they have demanded that you meet them halfway.  They don't offer everything up in a thirty-second commercial.  With "Looper," his work is no less dense or textured or intelligent than his earlier films, but he has finally made a movie that I feel offers up a complete experience, heady but deeply emotional, complex but easy to describe, demanding but equally rewarding.  "Looper" is more than just a stylish genre exercise… it is a moral argument wrapped up in a blockbuster's skin, a profound film that will engage audiences on many levels, and that will reward repeat exploration.

I saw a rough cut of the movie last year and at the time, I was very enthusiastic about the shape it was in.  The final coat of paint made a big difference, though, and I am deeply impressed by what Johnson's done here.  The film hinges on accepting a few big ideas that are introduced as part of the fabric of the world early on.  First, time travel is the mechanic that the film is built around, and as Joe (Joseph Gordon-Levitt) explains right at the start of the film, time travel has not been invented as of 2044, when the film begins, but it will be by 2074.  It's made illegal almost immediately, and the only people using it are criminal organizations who see a unique opportunity in using it.  Since disposing of dead bodies is a particular problem by 2074 thanks to tagging and digital tracking, they send a person back in time to a point where there is an assassin waiting, gun ready.  One shot, the body is incinerated, and the problem is solved.  The assassin didn't technically kill anyone who exists in their own timeline, and in the future, the person is just gone.  Joe is a Looper, as they're called, one of the killers, and he lives life as a blur.  He's learning French for a future he's fooling himself about, using a near-constant stream of drugs to numb himself to what he does for a living even as he socks away money that he tells himself he'll use when he retires.

The thing is, you don't really retire from being a Looper.  Instead, there comes a point where your future self is sent back and you kill them, thereby "closing your loop."  At that point, you're given a massive payday and sent off to live whatever life you want until that inevitable point in the future when you're going to be picked up and sent back to prevent you from spilling the beans on your employer.  It's a cold, impersonal system, but the Loopers all seem to be at peace with it.  Sure, there's an occasional hiccup in the system, and we see an example early on when Seth (Paul Dano) lets his future self run off.  That can't be allowed, though, and one of the most remarkable images in the film deals with how Seth's future self and present self are both dealt with by the organization headed by Abe (Jeff Daniels), the ones who assign the contracts to the Loopers.  Joe seems fine with the way things work, occasionally troubled by little bubbles of moral conscience, but for the most part happy to live his routine.  He fools himself into thinking he's got some connection to Suzie (Piper Perabo), a whore who he visits regularly, but the truth is, he's alone, and he's used to it.

All of that changes when Joe's older self is sent back and he tries to close his loop and fails.  Bruce Willis plays the older Joe, and in one stunning sequence, we see how Gordon-Levitt ages into Willis, a long montage in which we see those thirty years play out and we see the choices that lead from the man holding the gun to the man kneeling in front of it.  Willis escapes, determined to break the cycle by tracking down the person who will eventually order his death, determined to win back the existence that is so important to him, the life that he builds during those thirty years.  Gordon-Levitt wants to stop him, and there's a great scene in a diner between the two of them as they talk about the absurd situation they're in, laying out the stakes.  For Willis, everything boils down to the woman he eventually married, a woman he credits with saving his life.  He is disgusted by the person he used to be, barely able to disguise the contempt he has for his younger self.  For Gordon-Levitt, there's a sense of outrage that this old man would try to take those thirty years of life away from him, and he wants his older self die and let him live.  Willis tells him about "The Rainmaker," a terrifying figure in the future who is the one responsible for methodically killing all the Loopers, and Willis lays out his plan.  He's going to find The Rainmaker as a child and he's going to kill him, thereby securing his own future and keeping his wife safe and intact.

So in a sense, you can view this as "The Terminator," if Kyle Reese was both himself and the person hunting down Sarah Connor.  Gordon-Levitt realizes that the only way he's going to find and stop Willis is if he can get to the Rainmaker first and wait there until Willis arrives.  He doesn't count on the emotional impact of his encounter with Sara (Emily Blunt), the mother of one of the three children on Joe's list, or his own reaction to Cid (Pierce Gagnon), the little boy he eventually becomes determined to protect.  Putting the old Joe and the young Joe on a collision course, the film would probably be pretty great just as an action/sci-fi exercise.  The thing is, Johnson wants more from the movie, and thanks to the great performances and a carefully-structured screenplay, it's not just about the undeniably propulsive drive of that second act in the film.  Emily Blunt and the remarkably poised and professional Gagnon give the film a beating heart, and when Gordon-Levitt comes into contact with them, the film suddenly blooms into something very raw and emotional.  They are both tremendous here, and after seeing Blunt in so many comedies recently, it's a potent reminder that she is a powerhouse when it comes to drama as well.

Overall, it's a strong technical accomplishment, a science-fiction film with a well-realized sense of time and place, and everyone involved deserves praise.  The production design by Ed Verreaux is grounded and believable.  The score by Nathan Johnson is strong and spare.  Steve Yedlin's photography is slick, but also directly plays into the film's emotional side, and Bob Ducsay's editing is the same thing, technically impressive but also thematically grounded.  Kazuhiro Tsujji has to be mentioned for the work he did on the prosthetics that Gordon-Levitt wears for the whole film to make him look a little closer to Bruce Willis.  It's subtle work, focused mainly on the nose and on helping give Gordon-Levitt the same sort of perma-smirk that is Willis's trademark, but it never looks like make-up.  The first time I saw the film, it took me a little while to adjust to the alterations to Gordon-Levitt, but this time, I was impressed by just how careful the film is to make it look natural, and by how quickly I found myself unable to picture Gordon-Levitt out of the make-up.

I feel like any discussion of the film's second half would be unfair to an audience, so I'll just say that the longer the film plays, the more affecting it becomes, and it builds to a very simple conclusion that packs a huge wallop.  I was moved to tears by the film's very real belief in the importance of parenting and by the way it challenges the viewer to have their own reaction to the questions it poses.  I am deeply impressed by it overall, and I think when we talk about Joseph Gordon-Levitt as a movie star, "Looper" will be one of the key movies in that conversation.  Even if you're not a science-fiction fan, you should see this one.  It does what the very best of the genre does, transcending it to make important observations about who we are right now, who we want to be, and just how hard it is to be the best versions of ourselves.

"Looper" arrives in theaters September 28th.  Don't miss it.