When sad-sack Iowa gambler Gerry (Ben Mendelsohn) sits down at his regular poker game, he’s intrigued by a chatty stranger (Ryan Reynolds) who buys him top-shelf whiskey and serves up bottomless crowd-pleasing anecdotes.

Reynolds’ Curtis, a mysterious drifter, agrees to bring his new friend down to a high-stakes New Orleans game, where Gerry has a chance of winning back the money he seemingly owes everyone.

So far, so typical for a gambling-addict drama. But this low-budget indie has a unique ambiance and surprising depth, both in the performances of its two leads and the writing/directing team of Anna Boden and Ryan Fleck (“Half Nelson”). Sienna Miller and Analeigh Tipton, popping in briefly as good-hearted prostitutes, are actually human enough to subvert that dusty cliché as well — the plot keeps you off-kilter enough so you never quite know whether our adrenaline-hungry heroes will quit while they’re ahead or die trying.