In the opening shot, a tribesman walks through a rainforest with a child from the same tribe. They hear a loud rumbling noise. It's a bulldozer plowing through the forest.In the United States at Columbia University in New York City, we meet Justine (Lorenza Izzo), a college student. With her roommate Kaycee (Sky Ferreira), they sit through a lecture on the cruel traditions placed on women in African tribes, which horrifies Justine. Later, the two notice a group of janitors sitting for a hunger strike in order to obtain health insurance. The girls think these types of groups are stupid.After classes, Justine is invited by another student, named Jonah (Aaron Burns), to check out an activist group led by Alejandro (Ariel Levy). His cause is for the tribe in the Peruvian jungle. Justine makes a comment about the group starving themselves through the jungle for their cause, which Alejandro takes offense to. He orders Justine to leave.A few days later, Justine approaches Alejandro to apologize and decides she wants to join the cause. Another few days later, the two of them, plus a full group of activists, including Jonah, Alejandro's girlfriend Kara (Ignacia Allamand), Amy (Kirby Bliss Blanton), Amy's girlfriend Samantha (Magda Apanowicz), Lars (Daryl Sabara), and Daniel (Nicolas Martinez) head off on a flight, partially funded by Justine's dad, to Peru. Because the plane is small, it makes Amy anxious.Once the group arrives in Peru, they take a boat through the jungle toward their destination. They stop so Justine and Lars can use the bathroom. Lars almost gets his penis bitten by a tarantula and he runs back to the boat.When the group finds the bulldozers, they set off an explosive to stop their acts. As Alejandro recording the militia in their act against the jungle, one of the men holds Justine at gunpoint. Alejandro gets it on video to show off to the internet what kind of actions these people are willing to take against others, all while Justine cries. The man takes the gun away, and he and his men arrest the group.The group is being sent home in their plane. They celebrate their victory while Justine is traumatized from the incident and angry that the others were ready to let her get shot for their cause. Jonah announces that their video has been blowing up all over social media. All of a sudden, the plane's engine blows out, causing the pilots to lose control and head for a crash landing. The plane comes apart, sending at least two other people flying out. The plane crashes, killing both pilots. The man that flew out got impaled and the woman that fell out landed in a tree, badly injured and nearly dying. The rest of the group tries to move somewhere safe until they see some of the villagers in the forest. Kara asks them for help, but she gets an arrow in her neck. The others make a run for it, but they get hit by tranquilizing darts by unseen natives. Alejandro tries to remove the arrow out of Kara's neck, only for her to get another one in her head.When the group wakes up, they are being taken across the river by a Cannibal Headhunter, to the village where the rest of the tribe resides. They're all put in wooden cages, except for Jonah. He gets fed some kind of liquid before being laid down and having his limbs held down by some villagers. The Village Elder (Antonieta Pari) walks over to Jonah and holds a spike over his face. She digs the spike into his right eye and gouges it out before eating it in front of the villagers and Jonah's friends. The Elder proceeds to take his other eye, his tongue, and then has Jonah's limbs hacked off before he is finally decapitated. The others are horrified and cover their eyes.Jonah's remains are later cooked and soon eaten by the rest of the villagers. Alejandro determines that the villagers think they are the enemy. Lars mentions he can smell Jonah being cooked, making Amy sick. She first throws up and then has a massive bowel movement in the cage, which makes the others sick while the village children laugh and mock Amy.Justine tries to appease one of the children by playing her flute necklace that belonged to her mother. The child likes the music, but the Cannibal Headhunter and other native warriors arrive and pull Justine, Amy, and Samantha out of the cages. They take the ladies' panties off and the Elder takes a spike similar to what she used on Jonah. She puts it up Amy and Samantha's vaginas, then up Justine's. The Elder breaks Justine's hymen, proving to the tribe that she is a virgin. They take Justine into a hut and cover her in some kind of white powder before returning her to the cage.The next day, Alejandro mentions that the whole trip was just a PR stunt and that he doesn't actually give a shit about the tribe or the cause. He makes a crude comment on how it's good that Jonah was eaten first since he'd feed the tribe for a week, angering Daniel and Justine.Any attempt at escaping the cages leads to the group getting shot with darts by the watchers. They create a distraction that allows Samantha to climb out and look for help. Hours later, the villagers bring the group bowls with liquid and meat scraps. Amy drinks from the bowl and sea a bio-hazard symbol, which she recognizes as one of Samantha's tattoos. Then she sees the children wearing patches of flesh with the rest of Samantha's tattoos. Amy then smashes the bowl and slits her throat with a jagged piece.Knowing the villagers will get Amy next, Lars and Daniel stuff a bag of weed down her throat. the village Headhunter enters the cage and hacks Amy's corpse to pieces. After she is cooked and consumed, the villagers all get stoned. This allows Justine and Daniel to escape from their cage. Lars tries to follow but the cynical Alejandro gets him with a dart so he doesn't die alone.When Lars awakens, he sees two villagers sitting over him with the giggles. He tries to appease them with silly hand gestures until they start to get the munchies. One villager bites into Lars's arm, but he shoves him away and runs for it. Unfortunately, a large group of villagers attacks him and eats him alive.Justine and Daniel manage to get to a river and find some wreckage of the plane. Justine falls into the water and gets swept downriver. When Justine grabs a rock to hold onto, Daniel manages to rescue her by extending a tree branch and brings her ashore. That evening, they follow the trail of wreckage and finally arrive at the crash site of their plane. They find their GPS, but the battery's dead. They then hear a ringtone coming from the pocket of Kara, whose corpse is hung up alongside the other dead activists. Justine gets Kara's phone out of her pocket, but the villagers show up and dart her and Daniel.Justine awakens the next morning back in the village to find the medicine woman covering her nude body in white powder and paint. She is trying to sew Justine's vagina shut as part of a customary ritual. Daniel is tied up to a pole and covered from head to toe in a green mold by the village Headhunter. A colony of big ants start climbing up his body and biting into him. Before anything else happens to Justine, a child runs and brings the villagers the severed head of a man wearing a hard hat. The other villagers run out to see what other remains are available for consumption. The child that Justine played the flute necklace for shows up and unties Justine's hands. She unties her feet before the medicine woman returns. When she gets a good opportunity, she blows a special powder into the medicine woman's face and rips the bone out of her nose, allowing her to run. She tries to get Daniel, but he's in so much pain that he prefers to die. The child blows the powder in Daniel's face to make him pass out before he cuts Daniel's throat.The child leads Justine deep into the forest to escape. Alejandro begs Justine to save him, but she leaves him to the villagers. She lets the child keep the flute necklace and thanks him for helping her. Justine then runs and finds the militia shooting and killing the villagers. Justine finds the village Headhunter laying in the grass after being shot. With the local mercenaries approaching, Justine holds her hands up and states that she's American. She takes out Kara's phone and pretends to record the mercs in their acts before smashing the phone. The leader orders his men to take Justine away. She is boarded on a chopper to fly home, where she sees the bodies of the villagers sprawled everywhere and the soldiers burning the huts.Upon returning home, Justine testifies as the sole survivor from the crash. She denies witnessing any cannibalism.Justine then dreams that Alejandro made it home, and that she has monster teeth that she uses to rip out his throat. When she wakes up, she looks out her window and sees activists outside protesting for Alejandro to be returned home.During the closing credits, we hear a phone call between Justine and a woman claiming to be Alejandro's sister. She mentions seeing a surveillance photo (which we see) of Alejandro still in the jungle. His sister tells Justine that they need to talk.