Counter-intuitive casting is hardly original, but what is proposed by American Ultra intrigued me more than most: a comedy action movie with two young stars – Jesse Eisenberg and Kristen Stewart – whose generally serious screen personas would hardly suggest they’d be able to let their hair down (or flex their muscles) with the required abandon.

Though Eisenberg has appeared in the marvellous comedy Zombieland, he was essentially the straight man to Woody Harrelson; and the young star of the Twilight movies has bitten her lip through mostly earnest roles. But here they are, as a hapless stoner who happens to be a sleeper agent, but just doesn’t know it, and his long-suffering girlfriend with her own skill set more knowingly concealed.

And as it happens, the idea, the casting and their performances are the best thing about the film; if only it hadn’t been directed by someone who himself seems to have been working under the influence. It’s been a while since I’ve seen an action movie directed in such a low-rent and ham-fisted way.

Mike Howell (Eisenberg) is a small-town slacker, addicted to weed, who works at a cash and carry store where he idly spends his time drawing a comic strip about a space-travelling chimpanzee. When Mike decides to take girlfriend Phoebe (Stewart) on holiday to Hawaii in order to propose marriage, a panic attack stops him in his tracks; attempting to make a consolation supper, he almost burns the house down. Phoebe is much more together, and her affection for him is baffling.

Then one evening a woman walks into the store and speaks to Mike in a strange code that makes no sense to him. But later, when accosted by two violent men in the parking lot, he suddenly finds that he’s become quite deadly with a spoon.

The plot wastes no time in revealing that Mike is a leftover subject of a failed CIA experimental programme to produce lethal assassins. Now a power-hungry CIA operative (Topher Grace) has taken it upon himself to “clear the portfolio”, sending all hell down upon the town. Mike’s customer was a guardian angel, who has reactivated him so that he can protect himself.

Almost all of the pleasure comes from the leads. Eisenberg uses his very particular, straight-bat delivery to eke the most of the still-stoned Mike’s attempt to come to terms with his real identity, whether declaring that “I have a lot of anxiety about this” after taking out his would-be assassins, or with his constant concern that he might, in fact, be a robot.

Later, as their characters buckle under the pressure, he and Stewart lend the film an emotional charge that the genre generally isn’t used to, and this film doesn’t merit. The pair have appeared together before, in the comedy Adventureland, and have a rapport that creates some genuine romantic frisson amid the mayhem.

Sadly, around them the film is a mess. A couple of action scenes demonstrating Mike’s ingenious use of kitchen utensils work well enough, but much of the script is clunky (Grace’s CIA villain is appallingly written) and Nima Norizadeh’s direction is desperately unimaginative, with too many bland heavies routinely despatched in a shower of gore. In an age when we at least expect competence and some style from action movies, it’s just not good enough.

By coincidence, I happened to see Total Recall again recently, another film whose hero awakens to his true, lethal identity. Norizadeh should study Paul Verhoeven for a masterclass in how to deliver tongue-in-cheek and exciting action in one package.