The main characters in “Arthur Newman” want to change their identities, and they’re played by two excellent actors, Colin Firth and Emily Blunt. But this debut feature by Dante Ariola, a director of music videos who apparently wants to prove that he can eschew the energetic conventions of that form, makes you wish that Firth and Blunt had changed scripts instead.

Firth plays Wallace Avery, a sad-sack middle-management fellow tired of his life and despised by his teenage son (Lucas Hedges), who lives with his dismissive ex-wife. It’s no wonder that Wallace should seek to escape his miserable existence. So after securing a fake ID in the name of Arthur Newman from a forger (the venerable M. Emmet Walsh in a mere cameo), buying a new vehicle and somehow accumulating a bagful of cash, Avery fakes his drowning in a beach accident—a ploy reminiscent of “The Fall and Rise of Reginald Perrin,” though there it was played for dark humor.

But in Becky Johnston’s script it’s taken very seriously, and presently Wallace—er, Arthur—is on the road. But being a good guy, he almost immediately rescues a damsel in distress—one Michaela, or “Mike” Fitzgerald (Blunt), whom he takes to the hospital when he finds her in a bad state and then accepts as a passenger. It isn’t long before she discovers his imposture—though it takes him a lot longer to recognize that she’s using the name of her twin sister, who’s ensconced in a mental institution somewhere.

Nor does it take long for Arthur to spill the beans about his disappointing past. He was once a promising golfer, who choked on his first pro tour and never recovered. Now, he tells her, he’s off to Indiana, where a fellow he helped with his swing—and told he was a pro—has offered him a job on the links of his hotel.

Along the way Mike induces Arthur to join her in a curious game, breaking into the houses of couples while they’re away and adopting their identities, wearing the clothes they find there and pretending to be the owners. There’s the chance that despite the age difference they’ll stumble into a real romance—though Johnston and Ariola seem determined to keep matters relatively chaste, one montage apart. (After all, Arthur has previously chastised a motel clerk for having a television tuned to pornography where any customer could see it.)

Arthur and Mike travel a lot in the course of the movie, but the filmmakers apparently thought the story needed some contrasting element, so they periodically cut back to Avery’s son, his mother, and Wallace’s concerned girlfriend Mina (Anne Heche), with whom the boy begins to develop a fragile bond. These scenes frankly seem extraneous, though they’re presumably meant to suggest that Avery’s life wasn’t quite so empty after all. And there are plenty of references to golf, a motif that may be intended to suggest one should keep swinging even if the ball doesn’t always go into the hole—one gets not just second, but third and fourth chances.

Or maybe not. The problem with “Arthur Newman” is that the characters—both the real ones and the personalities they assume—never seem authentic. That’s why the film, despite its fine cast and technical quality—Edward Grau’s expert widescreen cinematography, Christopher Glass’s able production design and Nick Urata’s affecting score—doesn’t resonate emotionally, coming across as an artificial exercise about people who are synthetic in more ways than one.