The trailer for Greta might make you rethink ever being kind to a stranger in New York City again. It follows the young Frances, played by Chloë Grace Moretz, who finds a lost purse on the subway and, instead of heeding the many MTA announcements that implore anyone in this situation to tell a police officer or an MTA employee, goes to this perfect stranger’s house (!!!!) to return it. The bag’s owner, Greta, played by Isabelle Huppert, is a seemingly lonely older woman who soon entices Frances into a close friendship that escalates quickly into full stalking and lots of broken dishes and probably murder. While you shouldn’t let this scare you away from enjoying New York City’s crumbling public transit, let this be a reminder that we do have procedures in place for abandoned bags on the subway: If you see something, say something.