"I'm on a boat, I'm on a boat/Everybody look at me/'Cause I'm sailing on a boat."

“I’m on a boat, I’m on a boat/Everybody look at me/’Cause I’m sailing on a boat.”

The con movie is becoming a rite of passage for young Hollywood: Morally-challenged hot-shot is recruited by a villainous, powerful veteran to do his dirty work. Sooner or later, the kid realizes the error of his ways and sets his mind on cheating said mentor at his own game. Jim Sturgess in 21, Liam Hemsworth in Paranoia and Shia LaBeouf in Wall Street: Money Never Sleeps have gone through this initiation.

Interestingly enough, to this day, none of them seem able to carry a movie all by themselves.

Now is time for Justin Timberlake to take a turn at the bat. A recurrent presence of screen, big and small, JT has never opened a film alone (in Friends with Benefits and In Time he shared the lead with a love interest). In Runner Runner, Timberlake is Richie, a Princeton student who lost his fortune during the Wall Street debacle. Now he makes ends meet by peddling online gaming sites.

After losing his tuition money in a poker website, Richie becomes convinced the game was rigged, so he does the obvious thing: Travels to Costa Rica to confront the off-shore mastermind behind the scheme. The slick programmer (Ben Affleck as a grizzled veteran) convinces Richie to join his organization instead. Even though money begins to pour and the perks are incredible (Deadmau5-hosted parties!), Richie suspects there is something fishy about the whole operation. This doesn’t prevent him from bedding his boss’ girlfriend, but still.

For at least the first half, the movie is moderately entertaining, as debauchery often is. Then, as JT half-assed investigation advances, Runner Runner goes off the rails. In spite of the exotic location, most of the dramatic tension has to do with computers, not quite a cinematic scenario.

Director Brad Furman (The Lincoln Lawyer) fails to build a remotely cohesive denouement. It also wastes the comely British actress Gemma Arterton as mere decoration. Americans really don’t know what to do with Arterton, who is a fairly reliable presence in British films (Tamara Drewe, The Disappearance of Alice Creed), but has yet to do a watchable movie in Hollywood.

As for Ben Affleck, he is the sole bright spot here as the dissolute, chip-on-his-shoulder kingpin. By underplaying his hand, he comes out as believable. Still don’t have high hopes for his Batman, but he is not as bad an actor as we tend to assume. Two prairie card-sharks.