Detectives Jeb Pyre and Bill Taba investigate the brutal, sinister murders of an LDS woman, Brenda Wright Lafferty and her baby daughter in Utah’s typically serene Salt Lake Valley in 1984.

With a lead suspect in custody, the investigation uncovers more ominous questions than answers as the hidden history of the once admired Lafferty family is exposed.

The ongoing investigation leads Pyre and Taba into untrod woods where they unearth information that challenges Pyre's own faith, and draw more Laffertys into suspicion and custody.

The investigation intensifies after Pyre uncovers details of the Lafferty family's fundamentalist beliefs, sparking a search for missing Lafferty brothers, Ron and Dan, and putting Pyre at odds with his own church leaders.

With evidence now pointing squarely toward fundamentalist Mormonism, Pyre (Andrew Garfield) turns to LDS Church leaders for guidance but is met with roadblocks. Undeterred, he discovers a list of names Brenda's killers plan to murder next.

New details emerge about Brenda's attempt to reckon with some of the Lafferty family's most extreme members and beliefs, as Pyre and Taba hunt for those who killed Brenda before they can kill again.

As the details of the murders become clear, Pyre and Taba embark on an interstate manhunt, hoping to catch the killers before they complete their list of those to be "blood atoned."