Sierra Barter suspects her step-grandfather was a serial killer.

Jim Mordecai appeared as a friendly teacher to most, but was a monster to others; Sierra reflects on the path of escalation that Jim's crimes took.

Sierra's uncle shares a disturbing story about Jim; a private detective urges Sierra to search for evidence; Sierra learns a terrible truth while rummaging through family storage.

With advanced technology, Sierra builds a DNA profile of Jim; having compiled the necessary evidence, Sierra hands the files over to law enforcement in hopes they will investigate.