'Bad Samaritan' review: Promising thriller loses its grip

In “Bad Samaritan,” a restaurant valet named Sean Falco (Robert Sheehan) runs a slick scam: While customers dine, he drives to their houses, lifts a few valuables, then returns their cars with a smile. It’s the perfect low-stakes crime, until Sean burgles the house of the ostentatiously rich Cale Erendreich (David Tennant), and discovers, to his horror, a woman chained and gagged in a hidden room.

What can Sean do? He’s too good a guy to simply leave her, but there isn't time to free her before Cale finishes his meal. Should Sean call the police with an anonymous tip? Turn himself in? And if none of that works, what next?

That’s a question this potentially gripping thriller has trouble answering. "Bad Samaritan" has a ripping good premise, but not enough story to back it up. Despite a lively performance from Tennant as our villain and a rather soulful turn from Sheehan (a relative newcomer from Ireland) as our flawed hero, "Bad Samaritan" only partially delivers on its promise.

“Bad Samaritan” is directed by Dean Devlin, following last year’s big-budget disaster flick “Geostorm,” yet it still feels like an amateur outing. That’s partly due to Brandon Boyce’s screenplay, which starts strong but ends up weakened by plot holes. Some are big: What kind of neat-freak killer doesn’t notice his favorite tools are missing? Some are small: What kind of police detective does zero research on a new case? Others are absolutely gaping: Who’s the beautiful brunette Cale trots out as his too-perfect alibi? Guess we’ll never know.

Cale, by the way, is an awfully ill-explained character, even by movie-psycho standards. A crazed disciplinarian with a horse fetish and a sex phobia, he's a Freudian jambalaya of hang-ups and complexes. Tennant gives him a bit of personality — snippy, prissy, privileged — but he’s more irritating than frightening.

“Bad Samaritan" has its moments, though. The first appearance of the imprisoned woman (Kerry Condon) is a shocker even though we’ve been expecting it, and Sean’s attempts to redeem himself by doing the right thing keep us on his side. “Bad Samaritan” could have been a gem, if only it had put as much effort into its story as its setup.