JOPLIN, Mo. — Only three features in, Rian Johnson is fast establishing himself as one of the most dependable filmmakers working today. His latest, “Looper,” shows that he is continuing to grow as an artist.

At first glance, “Looper” looks like one of so many science fiction/time travel hybrids. In a not-so-distant dystopian future, Joe (Joseph Gordon-Levitt) is a looper, or paid assassin. The people he is contracted to kill are those transported from a slightly more distant dystopian future.

It seems that killing and disposing of the unwanted has become a little cumbersome, so the undesirables are transported back in time, where the looper waits and finishes them off with his blunderbuss. After each kill, the looper disposes of the body, then awaits his next charge.

There comes a point in each looper’s career where he must close his loop, or execute his future self. It is a lucrative kill, giving enough money to set the former assassin on the path to retirement. But when Joe’s future self is sent back for execution, Joe muffs the job, leaving old Joe (Bruce Willis) running free, trying to alter the course of the future by tracking down a despotic dictator well before he can assume power.

Joe’s boss (Jeff Daniels) doesn’t take too kindly to loopers failing to close their loops, so young Joe must evade his own death sentence while trying to finish the job he had been paid to do with old Joe.

What keeps “Looper” from being yet another generic sci-fi film is the intelligence behind Johnson’s script.

So many of these types of films trip themselves up over time travel logic, sometimes in minor ways, sometimes in ways that render the film utter nonsense (Men in Black 3).

Johnson has so carefully crafted his film that there is logic to every plot point and justification (and more importantly, a consequence) for every move that old Joe makes in his past.

In addition, Johnson does a wonderful job of pitting the young killer against his older self, each working toward their own purpose, and each man’s driving motivation conflicting with that of the other. It is a brilliant way of pitting self against self, and just about every contingency is well thought out.

The only sticking point in the movie is the end, which could have completely negated the plot of the film. But the journey getting to that point is so rewarding, and the ending so powerful, that the viewer is able to forgive what seems to be the only snag in the film.

Gordon-Levitt, wearing a prosthetic chin and wig to more closely approximate the actor portraying his older self, has far distanced himself from so many of the child actors who have tried to transition to more adult roles.

The first time he caught my attention in a more mature role was in Johnson’s first film, “Brick,” an amazing modern day film noir that required Gordon-Levitt to navigate tricky boilerplate dialogue without making it seem ridiculous. This time around, he must not only portray a character, but he must also approximate the actor playing his older self.

He captures the cocky arrogance, steely squint, sly smirk and unique speech pattern that Willis has carried throughout his film career. But he does so while still making Joe unique Ñ a harsh yet sympathetic man who has a heart in a career where such a thing is a liability.

Willis seems to have long ago decided that as long as the paycheck cashed, it mattered little what he starred in. Aside from the occasional spark of inspiration in films such as “Red,” he has relegated himself to cookie cutter action and drama films that do little to challenge him. But he has shown that when paired with the right-up-and-coming director (Quentin Tarantino in “Pulp Fiction,” M. Night Shyamalan in “The Sixth Sense” and “Unbreakable”), he can be reinvigorated, and Johnson does precisely that with Willis this time out.

Willis does an excellent job portraying the flip side to Gordon-Levitt’s coin Ñ the much older yin to his yang. After seeing him phone in his performance in “Expendables 2” this summer, it was refreshing to see a glimpse of the Willis of old.

But the true star of the film never appears on camera, as Johnson continues to prove that he is no fluke. Able to craft tricky, extraordinarily complicated scripts such as “Brick” and “The Brothers Bloom,” and realizing them behind the camera as the director, Johnson has defined himself as a voice to be reckoned with Ñ an auteur in a world of hacks and wannabes.

“Looper” is a winningly creative twist on what now feels like a well-worn genre, and Johnson just continues to show improvement.