Months after the death of their parents, grieving twins Sarah and Byron Hopewell and their closest friends embark on an end-of-summer getaway to the siblings' inherited home. The plan is to move forward; go into senior year with a fresh start. But unbeknownst to the teens, the emergence of a rare astrological occurrence will kick-start a fight for survival against the mysterious and violent harbingers of an evil being, with ties to the origins of humanity.