Brit Marling has carved a little niche for herself, co-writing scripts that she can star in. She has chosen a cousin of science fiction for her first two films, 2011’s Another Earth (about Earth’s encounter with a twin planet) and Sound of My Voice. Neither has a lot of visual effects or anything physical that would identify it as sci-fi; the genre is constructed purely through the narrative. In Sound of My Voice, she plays Maggie, a cult leader whose followers believe she has traveled back in time from 2054. She sounds a grave warning for our collective future, but Peter (Christopher Denham) and his girlfriend, Lorna (Nicole Vicius), don’t buy any of it and set out to expose Maggie as a fraud through a documentary they’re filming. It’s a great idea, but the film lacks a lot of definition of some pretty integral points.