In April 1992, Christopher McCandless arrives in a remote area just north of the Denali National Park and Preserve in Alaska. Noting McCandless’ unpreparedness, the stranger who drops him off gives him a pair of gumboots. McCandless travels into the wilderness and sets up a campsite in an abandoned city bus, which he calls “The Magic Bus.” At first, McCandless is content with the isolation, the beauty of nature around him, and the thrill of living off the land. He hunts with a .22 caliber rifle, reads books, and keeps a diary of his thoughts as he prepares himself for a new life in the wild.
Two years earlier, in May 1990, McCandless graduates with high honors from Emory University. Shortly afterwards, he rejects his conventional life by destroying all of his credit cards and identification documents. He donates nearly all of his savings to Oxfam and sets out on a cross-country drive in his Datsun 210 to experience life in the wilderness. McCandless does not tell his parents, Walt and Billie McCandless, or his sister Carine what he is doing or where he is going. He refuses to keep in touch with them after his departure, causing his parents to become increasingly anxious and eventually desperate.
At Lake Mead, McCandless’ car is caught in a flash flood, causing him to abandon it and begin hitchhiking. He burns what remains of his cash and assumes a new name: “Alexander Supertramp.” In Northern California, McCandless encounters a hippie couple named Jan Burres and Rainey. Rainey tells McCandless about his failing relationship with Jan, which McCandless helps rekindle. In September, McCandless arrives in Carthage, South Dakota and works for a contract harvesting company owned by Wayne Westerberg. He is forced to leave after Westerberg is arrested for satellite piracy.
McCandless then travels on the Colorado River and, though told by park rangers that he may not kayak down the river without a license, ignores their warnings and paddles downriver until he eventually arrives in Mexico. There, his kayak is lost in a dust storm, and he crosses back into the United States on foot. Unable to hitch a ride, he travels on freight trains to Los Angeles. Not long after arriving, however, he starts feeling “corrupted” by modern civilization and decides to leave. Later, he is forced to resume hitchhiking, after being beaten by railroad police.
In December 1991, McCandless arrives at Slab City, in the Imperial Valley, and encounters Jan and Rainey again. There, he also meets Tracy Tatro, a teenage girl who shows interest in McCandless, but he rejects her because she is underage. After the holidays, McCandless decides to continue heading for Alaska. One month later, camping near Salton City, McCandless encounters Ron Franz, a retired man who recounts the story of the loss of his family in a car accident while he was serving in the United States Army. He now occupies his time in a workshop as an amateur leather worker. Franz teaches McCandless the craft of leatherwork, resulting in the making of a belt that details McCandless’ travels. After spending two months with Franz, McCandless decides to leave for Alaska, despite this upsetting Franz, who has become quite close to McCandless. On a parting note, Franz gives McCandless his old camping and travel gear, along with the offer to adopt him as his grandchild, but McCandless simply tells him that they should discuss this after he returns from Alaska.
Four months later, at the abandoned bus, life for McCandless becomes harder, and he makes several poor decisions. As his supplies dwindle, he realizes that nature is also harsh and uncaring. McCandless concludes that true happiness can only be found when shared with others, and he seeks to return from the wild to his friends and family. However, he finds that the stream he had crossed during the winter has become wide, deep, and violent due to the snow thaw, and he is unable to cross. Saddened, he returns to the bus. In a desperate act, McCandless is forced to gather and eat roots and plants. He confuses similar plants and eats a poisonous one, falling sick as a result. Slowly dying, he continues to document his process of self-realization and imagines what it might have looked like if he had managed to return to his family. He writes a farewell letter to the world and crawls into his sleeping bag to die.
An epilogue states that two weeks later, his body is found by moose hunters. Shortly afterwards, Carine returns to Virginia with her brother’s ashes in her backpack.