There's something sinister under the surface of the idyllic, suburban town of Wesley Falls, and it's not just the abandoned coal mine that lies beneath it. The summer of 1995 kicks off with a party in the mine where six high school students witness a crime that changes the course of their lives. When they realize they can't trust anyone but each other, they begin to investigate what happened on their own. As tensions escalate in town to a breaking point, the six make a vow of silence, bury all their evidence, and promise to never contact each other again. Twenty years later, Maddy has been murdered, and to end things they have to return to the mine one last time.