**1/2 (out of four)
You can pretend you haven't, or you can just admit it -- everyone's seen one of those late-night thrillers on Cinemax rife with low-budget murders and soft-core intimacy.
Taking time off from his casual, mostly improvised observations of relationships ("Drinking Buddies," "Nights and Weekends"), Chicago writer-director Joe Swanberg maintains focus on the gaps that exist between couples even as he tackles an erotic mystery. Fetish photographer Billy (Adam Wingard, who directed Swanberg in "You're Next") can't help but drift over intangible lines when he chooses models based on attraction, something that inevitably causes problems with his girlfriend/colleague, Alex (Caroline White). Perhaps the couple asks for it by engaging in a threesome with Callie (Anna Kendrick look-alike Sophia Takal), but Billy doesn't know what he's getting into with Rebecca (Helen Rogers) and her jealous boyfriend. Or maybe he's too drawn to her to care. As all this lust swirls, an unhappy detective ("You're Next" writer Simon Barrett) investigates the murder of a young woman.