One of the most eagerly anticipated movies coming in fall is Looper, a time travel gangster flick from Rian Johnson (director of cult favorite Brick), starring Joseph Gordon-Levitt and Bruce Willis. Last weekend at Comic Con, we had a chance to sit down with Johnson and ask about his theory of time travel, as well as why this scifi trope fits so well into a gangster movie. His answers made us more excited than ever to see this weird twist on traditional time travel tales.

Looper takes place 30 years in the future, where a hit man called a "looper" (Gordon-Leavitt) works for a mob that exists 60 years in the future. The future mob sends its marks back to Gordon-Leavitt's time, where the looper shoots them and disposes of the bodies — it's the perfect way for the future mobsters to commit murder and leave no trace. The problem? One day, Gordon-Levitt's future self comes through the time portal, and the looper is too surprised to finish the hit. So he has to track himself down in a bizarre cross-temporal suicide mob assassination. You can watch the video to see Johnson in action, or just read our interview below.

io9: What is your theory of time travel?

Rian Johnson: Basically the movie takes the approach the first Terminator movie took, where time travel technology exists in the future but it doesn't exist in the present where our movie takes place. So none of our characters actually use it. They just deal with this thing sent back from it.

Why Looper Could be the Most Well Thought-Out Time Travel Movie in YearsAlso, they work for a mob — they're thugs. We don't have the scientist character, we don't have the chalkboard where somebody explains to them how it works. They're kind of just doing their best. When Joe's older self shows up and he lets him run, there is probably terrible stuff happening in the timestream, and you see some of the effects of that in the movie. But you never step outside these characters' perspectives. They have to just deal with what's right in front of them.

Johnson also told us that he spent a lot of time coming up with the mechanics of how the time travel worked, and created a lot of diagrams. He may reveal these after the movie comes out.

io9: What does the near future world look like?

Rian Johnson: It's a dystopian future we've seen before to some degree, and that was intentional because there are a lot of big concepts in the movie with time travel and with the story between Bruce and Joe. There's a lot of stuff to wrap your head around so the movie wasn't about creating a unique futuristic environment. The dystopian element serves its characters really well because everyone's fighting to keep their little corner of whatever they've got because the world's in such bad shape.

Why Looper Could be the Most Well Thought-Out Time Travel Movie in YearsWe never address [what caused the dystopia]. That came up a couple of times and I really resisted — I was like, "You know what? It's not that difficult to imagine something happening in the next 30 years that throws the world into a bad spot." There's a thousand things it could be and the movie is about none of them.

We were gunning for a believable world. More often than not, I was pulling the designers back. With the guns, there would be this huge gun in the first design pass that looked like something out of Halo and I said, "That's an awesome scifi gun, but let's pare it way down and make it look like a metal shipping tube," basically. Let's see how simple we can make this stuff. How grounded we can make it. That to me was more interesting than dousing it in scifi design stuff.

Johnson told us that the film's distributors, a Chinese company, offered him money to film several futuristic scenes in Shanghai. Originally, they had planned to film these scenes in Paris, but there wasn't enough money in the budget to do much more than pretend New Orleans was Paris. Johnson felt that the offer from his Chinese distributors helped the film fit into a common idea about the future, which is that Asian megacities will be tomorrow's lands of opportunity. We see Shanghai in some flash-forward sequences where Gordon-Levitt's character goes to make his fortune.

io9: Why do time travel and crime go so well together?

Rian Johnson: One of the basic appealing things about time travel is being able to step out of this tiemeline we're all chained to, of birth to death and "this is the time you've got and that's it." So there's soemthing about cheating that's at the heart of the appeal that makes time travel this shiny object that we love considering in our heads. So there's something illicit about it, something that feels at its core like you're cheating something, like you're getting out of what you're supposed to have. It also is just the perfect way to steal something, from Time Bandits onward, to drop out of the sky and grab Napoleon's shit and then disappear again.

What's next for Johnson? He's working on writing a couple of features, one of which might be science fiction. After directing an episode of Breaking Bad this past season, he's hoping to do more TV. "I'd love to do an episode of Game of Thrones," he confessed. We'd love that too.

Looper hits theaters September 28.