In early 1980s, an Israeli adventurer named Yossi Ghinsberg (Daniel Radcliffe) travels to Bolivia for a journey into the heart of the Amazon rainforest. There, he meets Marcus Stamm, a Swiss school teacher, and Marcus's friend Kevin Gale, an American hiker and avid photographer. The three are staying in La Paz, where one of them has an apartment. Yossi is out in the market one day and a stranger asks if he is an American, he replied "No". This stranger is Austrian, Karl Ruprechter. During conversation Karl claims the existence of an Indian tribe in the jungle that they should go see. Karl says everything will be okay because he knows the jungle and he's friends with the tribe. Yossi, excited about the prospect of exploring the jungle, chooses to believe him. He heads back to the apartment to convince Marcus and Kevin to come along. Being skeptical of the stranger and his story, they refuse. Yossi continues to press them and they ultimately acquiesce.

The next day they meet Karl in a shop while he is gathering supplies for the hike. All three men are surprised when Karl leaves with the supplies and tells them they will pay for everything.

Yossi, Marcus, Kevin and Karl hike through the jungle for several days. They make it to a village where it's apparent Karl knows the villagers. They spend the day in the village and stay over night. They head back into the jungle the next morning. Marcus starts having trouble walking and it is discovered his feet are full of bloody sores. By now Kevin and Yossi are a little tired of Marcus' complaining. Yossi, Kevin and Karl are discussing how they all should proceed. Karl wants to leave the three while he goes and gets help but Kevin and Yossi disagree with that. At this point Marcus walks up and Kevin suggest an idea of building a raft and use the river so all of them can stay together. They build a raft and set off down the river. They hit some rapids, barely making it through. Karl gets upset at Kevin for taking control on the raft and floats the raft to shore and says something "smart" then says he's going hunting. Kevin noticed that Karl was afraid of water and can't swim. The gut feeling led them for their later survival. Yossi goes to find him so he doesn't leave them. Marcus and Karl decide to leave the journey and go back to La Paz, which takes three days. Yossi and Kevin continue their journey until their makeshift raft is destroyed by a strong current, and Yossi is washed away by the river, leaving Kevin behind. Without a knife or any kind of survival training, he must improvise shelter and forage to survive. Ghinsberg begins to give up hope after losing all sense of direction, wondering if he will ever survive the jungle. Meanwhile, Kevin is discovered by people from the local town who take him to Rurrenabaque which is 120 miles from Yossi's location, Curiplaya. Arriving there, Kevin called for the help of the local authorities to find Yossi. They failed to find Yossi through a plane flyover, but Kevin believes that Yossi is alive. Kevin ropes in the help of the local boat driver to search for him. Kevin finally discovers a now-weak Yossi and takes him to Rurrenabaque.

The epilogue says that Karl and Marcus were never seen again and Karl was wanted by the authorities.

https://en.wikipedia.org/wiki/Jungle_(2017_film)
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