When high school student Cassie Stoddart is found stabbed to death in a house on the outskirts of Pocatello, Idaho, the community is gripped by fear that a random killer is on the loose. Police retrace Cassie's final hours and focus on three classmates that were the last people to see her alive. As the investigation narrows, detectives uncover a shocking buried video tape that reframes the case, raising the unthinkable question of whether 16-year-olds could have committed such a brutal crime.