This investigative doc prods into a profoundly mysterious social cavity—the case of Joyce Vincent, a 38-year-old woman whose skeletonized corpse was found in her London flat a full three years after she had died. How she died is a mystery (not enough of her was left to tell), but as a pressing question it’s trumped by this: How could no one have noticed her absence, or smelt her decay, or even turned off her power? (The TV was blaring the whole time.) A paradigmatic parable about urban alienation and the modern eradication of community, the Vincent story gives director Morley a problem she can’t solve, and so the film is a self-mirroring enigma; the lack of facts becomes thematic. Surprisingly, given the setup, the half-Caribbean Vincent was no asocial shut-in, but a vivacious if skittish woman with a tumultuous love life. Morley interviews scores of acquaintances and ex-boyfriends, none of whom had known Vincent’s fate before the filmmaker called. (The dead woman also had four sisters, all of whom refuse to be filmed.) Left with barely any there there, Morley compensates with long reenactments starring look-alike Zawe Ashton that are never quite convincing but instead suck more air out of the haunting vacuum left behind in Vincent’s wake.