Madeline (newcomer Helena Howard) is a teenage girl who joins an experimental improv theater group, where she soon begins to shine. Evangeline, the workshop’s ambitious and manipulative artistic director (Molly Parker, American Pastoral, “Lost in Space”) takes an interest in Madeline’s raw talent, pushing the teenager to weave her rich interior world and troubled history with her insecure mother (Miranda July, Me and You and Everyone We Know) into their collective art. However, both Madeline and Evangeline get carried away, and the lines between performance and reality begin to blur, approaching madness. The resulting battle between imagination and appropriation rips out of the rehearsal space and through all three women’s lives. Anchored by a blazing virtuoso performance from Howard, whose powerful screen presence commands attention, writer/director Josephine Decker’s unique film displays a rare sensitivity for capturing the messy struggles of discovering a sense of one’s self that defies easy narrative categorization.