Medical students begin to explore the realm of near death experiences, hoping for insights. Each has their heart stopped and is revived. They begin having flashes of walking nightmares from their childhood, reflecting sins they committed or had committed against them. The experiences continue to intensify, and they begin to be physically beaten by their visions as they try and go deeper into the death experience to find a cure.

2002: Ray Kasten (Chiwetel Ejiofor) and Jess Cobb (Julia Roberts) are two investigators in a private police unit led by the DA. When they receive an anonymous tip about a girl raped and killed, they rush to the scene. Ray realizes it is Jess' daughter and the team falls apart due to the grief. In 2015, Ray comes back to LA, and says that after 13 years, he has found a lead and convinces the DA to reopen the case. They find clues and leads unknown to them, and secrets from the past come to light as they start discovering the real, chilling truth. Meanwhile, Jess, dissatisfied with the law, decides to take matters into her own hands and track down the killer, no matter what lengths she has to go to.