Vermilion Parish, Louisiana, 1995. Detectives Martin Hart (Woody Harrelson) and Rustin Cohle (Matthew McConaughey) investigate the ritualistic murder of former prostitute Dora Kelly Lange, found in a still smoking field of burned crops, with a symbol painted on her back and wearing a "crown" of deer antlers, blindfolded and posed as if praying to a large solitary tree. Numerous twig latticeworks, like Cajun bird traps, are found with her body in and around the field. Cohle is convinced that this is not the killer's first victim, but Hart is skeptical. Cohle is a new addition to CID and his aloofness and mysterious background makes the other detectives distrustful and hostile towards him, nearly leading to a fight with Detective Geraci (Michael Harney). Their investigation brings up the case of Marie Fontenot, a little girl whose disappearance five years earlier was not investigated. Another report is brought up of a child who claimed to be chased through the woods by a "green-eared spaghetti monster." Hart invites Cohle over for dinner, unaware that it is Cohle's deceased daughter's birthday. Cohle reluctantly accepts, but, losing a battle with alcoholism, turns up drunk. Hart and Cohle follow up on the Fontenot disappearance with a visit to Marie's uncle Danny. In a dilapidated playhouse, Cohle finds another twig latticework.
Seventeen years later, Cohle and Hart are interviewed separately, five days apart, about Dora Kelly Lange by Detectives Thomas Papania (Tory Kittles) and Maynard Gilbough (Michael Potts). Hart and Cohle have not spoken since a falling-out in 2002. Cohle is shown a photograph of another girl whose body has been found posed in similar fashion to Lange. Papania and Gilbough want to know how the killer could have struck again if he was caught in 1995.