“When I lived in Las Vegas, I had plenty of luck. The trouble is, most of it was bad.” So John Alighieri (Steve Buscemi) introduces himself in voiceover at the beginning of Saint John of Las Vegas—and, yes, the film is in fact loosely “inspired” by Dante, complete with a guide named Virgil (Romany Malco). Writer/director Hue Rhodes’s debut doesn’t really do anything with the reference point besides hope some gravitas rubs off. In detailing the long, weird odyssey of car-insurance employee John through his first fraud investigation, Rhodes watches as Buscemi—his eyes more sunken-in and cadaverous than usual—comes to terms with his gambling addiction and the no-shit revelation that, like many men, he’s destined for comfortable mediocrity. Getting to that point requires a putatively wacky journey through the southwest with sullen Virgil—the fraud investigator showing him the ropes, whose motives remain unclear—that veers between occasional laughs and portentous drama. As for Dante: Does a carny whose fire-suit keeps randomly lighting on fire (Harold Cho) count as suitably purgatorial? Mostly, Saint John traps good comic performers—including Malco and Peter Dinklage as John’s boss—in airless editing and an unproductive, unresolved, sludgy tone.