An overlooked detail provides Hart and Cohle with an important new lead in their 17-year-old case.

Hart and Cohle hunt for their newly identified suspect, Reggie Ledoux, a meth cooker who shared a cell with Dora Lange's husband and recently skipped parole. As Hart's personal life collapses around him, Cohle immerses himself in an old criminal identity from his narco days, contacting an East-Texas biker gang known to deal with their primary suspect.

A violent denouement in the forest clears the Dora Lange case and turns Cohle and Hart into local heroes. Each man settles into a healthier rhythm of living as Hart returns to his family, and Cohle starts a relationship while gaining a reputation as a closer in interrogations. As time passes and his daughters grow older, Hart faces new tensions and temptations, and Cohle learns from a double-murder suspect that there could be much more to an old case than he'd once thought. In 2012, Gilbough and Papania put their cards on the table, presenting new intelligence that threatens Cohle and causes Hart to reassess everything he thought he knew about his former partner.

Maggie reveals Cohle's activities in 2002, when his relationship with Hart fractured and he quit the force.

Hart and Cohle call a truce to investigate a series of disappearances that may be related to the Dora Lange murder and the Tuttle family.

A hidden image at the burned-out church leads Cohle and Hart to Joel Theriot, a tent-revival minister whose parishioners finger a scarred “tall man” seen with Dora Lange. Brought in for interrogation, a sex offender matching the description is quickly dismissed by Cohle, despite offering a confession. Hart gets sidetracked after Maggie sets Cohle up with a friend at a C&W bar. Looking to establish a pattern of murder, Cohle pores over old case files, finding a connection with a woman assumed to have drowned years earlier.

Former Louisiana State CID partners Martin Hart and Rustin Cohle give separate statements to a pair of investigators about the murder of a prostitute, Dora Lange, 17 years earlier. As they look back, details of the crime, replete with occult overtones, are accompanied by insights into the detectives’ volatile partnership and personal lives.

Under pressure to land a suspect in the Lange murder, Quesada warns Hart and Cohle that they might be replaced by three detectives from a new task force. The pair lobbies for extra time to follow up on a lead that takes them from a rural cathouse to an incinerated church. With his marriage to Maggie already strained by work, Hart finds respite away from home.

The disappearance of a young Arkansas boy and his sister in 1980 triggers vivid memories and enduring questions for retired detective Wayne Hays, who worked the case 35 years before with partner Roland West. What started as a routine case becomes a long journey to dissect and make sense of the crime.

In the midst of a brutal storm, Danvers and Navarro find themselves stuck at Tsalal with no electricity or means of contact. As the truth about what happened to Annie and the Tsalal men unfolds, Navarro and Danvers each confront the demons from their past.

When Julia's mental health struggles resurface, Navarro brings her to a local facility, promising that this time will be better. Later, Danvers and Navarro confirm the location of Annie's murder, and Danvers levies a harsh punishment on Leah.

The repercussions from Caspar's murder are felt by Frank and the Vinci Mayor's office. Ray and Ani are involved in a close call with the killer.

While Hank leads the search for Clark, Prior asks Danvers about the murder-suicide case that drove a wedge between her and Navarro. Then, Navarro and Danvers seek out a local hairdresser for insight on Annie -- which leads to a tip.

The disappearance of a city manager disrupts a lucrative land scheme and ignites an investigation involving three police officers and a career criminal who is moving into legitimate business.

Ben Caspar's autopsy reveals the gruesome details of his demise, and Ray and Ani wonder if it has anything to do with his fondness for prostitutes. Meanwhile, Frank looks into what might have happened to his missing fortune.

When eight researchers at Tsalal Station vanish without a trace, Danvers orders a search. After handling a workplace dispute, Navarro tries to convince a skeptical Danvers that the men's disappearance is connected to the murder of a local activist.

As Danvers and Prior learn more about Tsalal – and find an unlikely location for the physical evidence – Captain Connelly threatens to move the case to Anchorage. Later, Navarro and Danvers find a connection between one of the Tsalal men and Annie.

Ray and Frank contemplate new life choices. Ani and Paul follow a lead up the coast.