Two Madrid homicide detectives, Raúl Arévalo and Javier Gutiérrez, are dispatched in 1980 to a backwater town on the Guadalquivir Marshes, a remote pocket of Spain's Deep South, to investigate the disappearance of two teenage sisters, Carmen and Estrella, during the town's festivities.
Pedro Suárez, openly critical of Spain's Francoist past and distrustful of authority, clashes with the local power structure, while Juan Robles appears more detached but carries a troubled history of his own.
Rodrigo, Antonio de la Torre, the riverboat skipper, and Rocío, Nerea Barros, tell the detectives that their daughters were ordinary, even as the police describe them as promiscuous; Rocío also hands over a burnt film reel that shows the girls naked in bed with a man whose face is obscured by a flash.
Soon Carmen and Estrella are found dead, dumped in the marsh, having been raped and tortured. The investigation tightens its focus on Quini, the handsome former boyfriend of Carmen, who is now dating Marina, Ana Tomeno. When a drunk man named Castro mentions a similar case—the dismemberment of Beatriz, his girlfriend—the detectives sense a larger pattern at work.
As they press on, the detectives uncover a web of heroin smuggling tied to the riverboats and the marshes. Rodrigo had stolen a kilo and sold it, drawing the ire of locals involved in the drug trade who insist they had nothing to do with the sisters' deaths. A clue surfaces about a white Dyane 6 seen near a church where one girl's purse was found, and the case begins to point toward a broader conspiracy.
Digging through more victims’ items, a pattern emerges: out-of-town job brochures for young women who want to leave the town, circulated by a man named Sebastián. A past warrant against Sebastián for possible child molestation strengthens the suspicion that he is central to the operation. The detectives deduce that Quini and Sebastián lure vulnerable girls with the brochures and trap them at a hunting lodge.
The investigation grows murky as Pedro confronts the reality of Juan's past—his involvement in shooting a girl at a protest during the Franco era—and the possibility that Alfonso Corrales, a local factory owner, is a political shield behind the scenes. Nevertheless, the trio presses forward, eventually identifying Sebastián as the watchman of the hunting lodge.
Pedro attempts to tail Sebastián in his white Dyane 6 but loses him. With the aid of Salva Reina as Jesús, a local poacher, they corner Sebastián in the marshes. In a brutal confrontation, Sebastián shoots all three of them; Juan manages to stab Sebastián repeatedly, killing him as he falls into the swamp, and he frees a bruised but alive Marina from the trunk of a car.
Peace settles over the town as the case nears its end, and the workers’ union gains a promised pay raise. Pedro anticipates a promotion and a relocation closer to his wife, but the morning after, a journalist—Manolo Solo as Periodista—reveals that the case’s insider was not merely a bystander but a brutal officer from Franco’s secret police, once nicknamed “The Crow.”
As they drive away toward an uncertain future, Juan asks if they are “good.” Pedro remains silent, and the two depart together into the dawn, the truth hanging in the air and the road ahead uncertain.
