Watch 123Movies. In Grace Arbor the answers are never clear. Who is underneath the mask? This is the story of a group of high school kids - all popular, good looking, "most likely to succeed" types - who amuse themselves by pulling pranks on unsuspecting students and teachers. At their core lies a cruelty and shallowness which comes with the territory of privilege. One night, a prank goes horribly wrong, a teenager is killed, and the gang covers it up as a drowning accident but five years later, their lives are turned upside down when a local is killed by a serial killer wearing a haunting Marilyn Monroe mask. Soon, the gang are killed one by one in manners mirroring the pranks they pulled in high school. Is it revenge? Is it karma?