“Looper” is a mildly entertaining time travel sci-fi film with three likable stars: Bruce Willis, Joseph Gordon-Levitt and Emily Blunt.

Time travel is often used as a gimmicky crutch, as in the TV series “Lost.” To build a whole movie around time travel is risky. When a character interacts with his older self, things can get confusing. Gordon-Levitt and Willis play the same character, Joe, at different ages.

The movie is set in a not-especially-futuristic-looking 2044. Most of their vehicles appear about the same as those we drive today—except for that one cool jet-powered scooter. In 2044, time travel has not yet been developed. But 30 years beyond, time travel has been perfected. But it’s only used by the bad guys.

Because, we are told, it’s hard to dispose of human bodies in 2074, mob hits are accomplished by sending the poor suckers back to 2044 where they are quickly offed and tossed into a furnace. Among those sent back to be killed are older versions of some of those young assassins. They “loop” back, hence the title.

One looper who is sent back—the older Joe—escapes death at the hand of his younger self. He begins a mission to kill a 2044 vintage kid, before he grows up to become a gang leader called The Rainmaker. Still with me? This is where Emily Blunt comes in. She is a single mom, living in a rural farm house with her precocious child. Her kid may the one who would become the Rainmaker. The boy does have some mighty anger issues!

Jeff Daniels gives a standout performance as a crime boss with a wicked sense of humor.

Joseph Gordon-Levitt’s strange makeup (presumably to make him even slightly resemble Bruce Willis) gives him odd-looking lips and eyes. Emily Blunt sounds like a native-born American, squelching her limey accent.

“Looper’s” plot is messy. The movie’s pace hits the brakes just past its midway point. And the sci-fi lacks those “oh, wow” effects/settings/technology that you expect in a movie like this one.

“Looper” is not a bad movie, just one that needs more truly compelling content. One might presume that writer/director Rian Johnson figured the time travel bit might be a strong enough frame to build the movie on. Not quite.