On a seemingly normal vacation in Brazil, three young American tourists, Alex, his sister Bea and a friend Amy backpacking decide to go by bus and sightsee portions of the country, instead of flying directly to the Northeastern beaches they wish to visit. After a bus crash they are joined by two British men, Finn and Liam and the Australian Pru Stagler and head to the beach looking for a bar. There they get involved in a party with locals but are served drugged drinks and pass out. The next morning, they awaken on the deserted beach, with only the clothes they had on, stripped of luggage, money, and documents. Looking for help in the nearby village, they encounter conflict with locals as they see some of their belongings worn or lying around. Offering help, Kiko, a local who speaks some English, volunteers to take them to an isolated cabin in the forest, where they can wait for help. In a long walk through the wilderness, Kiko shows them a cave beneath a waterfall, but, taking a bad dive into the river, Kiko hits the rocky bottom, and is rendered unconscious and begins bleeding profusely from a cut in his head. Proceeding to the cabin in the jungle, they find food, clothes, and prescription drugs in a number of different names and a drawer filled with other people’s passports.They are awakened in the middle of the night by a helicopter bringing Zamora, a physician, and a few associates. They are advised to flee, because Zamora has twisted plans for them, but they are beaten into compliance. Zamora proceeds to a makeshift operating room where he removes organs from Amy, who is sedated, while he explains to Finn, who is tied up, that organ theft for transplant from Brazilians by rich gringos is part of a pattern of exploitation of Brazilian “resources,” and that it is time to “give back.” Victims' usable organs are being harvested and sent to the People’s Hospital in Rio de Janeiro and used for the benefit of the poor.
Meanwhile, the rest of the group outside manage to break free of their cages, fighting and killing one of Zamora’s associates. Alex sends Bea and Pru to wait by the waterfall they passed on the way to the remote residence. Then, he and Liam attempt to raid the cabin. They successfully rescue Finn, who is partially unable to walk because he has been sedated, but while they are running away from the cabin, Finn is shot in the head. Alex realizes they have to resume their escape, but Liam, incensed by the death of his friend, decides to stay behind and fight back, and he is killed.
By the waterfall, Alex, Bea and Pru try to hide inside the flooded cave Kiko showed them, eluding one of Zamora’s associates who is trailing close behind, armed with a bow and arrows, and Zamora’s party. For a time, they are able to put some distance between them and their pursuers. Diving and swimming to the cavern's secondary entrance, they find Zamora is already there, and he shoots them in the water, killing Kiko and injuring Alex.
The survivors are forced to backtrack into the water of the cave, where they can take air at only a few places. They split up, looking for breathing points, trying not to be noticed and fall prey to the archer. Bea and the archer meet at the same breathing spot, but Bea grabs an arrow from the man, stabbing him in the neck and killing him. Alex, Bea and Pru get out of the cave only to run into Zamora. Alex goes berserk, jumps Zamora and hits him in the head with a rock.
Alex is interrupted by the arrival of one of Zamora’s associates, who is armed with a rifle. Zamora instructs him to kill the foreigners. Seeing the trio of survivors, vulnerable and scared, and Zamora in agony, the man hesitates. This infuriates Zamora, who orders the gunman, in derogatory terms, to carry out the killing. Either because of the insult or the objectionable nature of the order or both, the man shoots Zamora and flees. The survivors, coming out of the jungle, meet local villagers who help them to recover.Later, Alex and Bea stand in line, waiting to board an airplane, while a couple of tourists behind them argue over going by bus. Alex advises them, “Take the plane.”