Writer-director Sebastian Silva’s film focuses on three close friends living in Fort Greene, Brooklyn: Freddy (Silva), a mercurial artist working on a baby-themed video-art project called “Nasty Baby”; his boyfriend, Mo (Tunde Adebimpe); and Polly (Kristen Wiig), who’s focused on having a baby, using Freddy’s sperm. When Freddy’s little guys aren’t up to the task, she asks Mo to help. The three struggle with how to define their relationship, and what it means to add a baby, while outside the brownstone, the little ad hoc family comes in for increasingly angry abuse from a mentally ill neighbor known as The Bishop (Reg E. Cathey). Silva’s work is deceptively low-key at first, finding space between shaggy character study and mildly jaundiced look at these self-absorbed sorts. But it helps to pay attention — the idle chatter, small slights and emotional patterns of the films’ first two-thirds are the critical clues for processing what comes next. It’s an act of violence that switches this film up from a noodling dramedy into something much darker and more complicated.