The film unfolds through a nonlinear narrative, oscillating between Christopher McCandless' adventures in the Alaskan wilderness and the two years preceding his fateful journey.
In April 1992, Christopher McCandless makes his way to a secluded area just north of Denali National Park and Preserve in Alaska. A kind stranger, recognizing Chris’ lack of preparation, offers him a pair of boots to aid his journey. As McCandless ventures deeper into the wild, he sets up camp in an abandoned bus he dubs "The Magic Bus". Initially, he embraces the solitude, captivated by the breathtaking beauty of nature and the exhilarating experience of living off the land. He hunts with a .22 caliber rifle, indulges in reading, and meticulously documents his thoughts in a diary, all while dreaming of a new life in the wild.
Fast forward two years to May 1990: McCandless graduates with high honors from Emory University. In a radical move, he rejects societal norms by destroying his credit cards and identification. He donates the majority of his savings to Oxfam and embarks on a cross-country drive in his Datsun B210, seeking to live free in the wilderness. He deliberately cuts ties with his family—his parents, Walt and Billie McCandless, and his sister, Carine—leaving them in the dark about his whereabouts, which leaves them increasingly anxious and desperate.
At Lake Mead, unexpected circumstances lead to his car being caught in a flash flood, prompting him to abandon it and start hitchhiking. He burns the remains of his cash and reinvents himself as "Alexander Supertramp." In Northern California, he encounters Jan Burres (Catherine Keener) and her partner Rainey, where he helps mend their troubled relationship.
Later, in September, McCandless finds work with a harvesting company owned by Wayne Westerberg (Vince Vaughn). However, he must leave when Westerberg is arrested. His journey continues as he navigates the Colorado River, defying park rangers by kayaking without a license and ultimately finding himself in Mexico. After his kayak gets lost in a dust storm, he retraces his steps back into the U.S., where he travels by freight trains to Los Angeles. However, he soon feels disillusioned by the corrupting influence of modern civilization and departs once again.
By December 1991, McCandless winds up in Slab City, California, where he reunites with Jan and Rainey, and meets Tracy Tatro (Kristen Stewart), a girl interested in him, whom he respectfully declines due to her age. After the holiday season, he resolves to continue toward Alaska. A month later, while camping near Salton City, he meets Ron Franz (Hal Holbrook), a retired man who shares the profound pain of losing his family. Graciously, Franz teaches McCandless leather-working, creating a belt that chronicles his journey before he ultimately departs for Alaska, despite Franz's heartbreaking plea to stay.
As the months pass, living in the bus becomes increasingly challenging for McCandless. He encounters the harsh realities of nature, with dwindling supplies leading to dire choices. It dawns on him that true happiness cannot be experienced in isolation; instead, it thrives in connection with others. Unfortunately, his attempt to return to civilization is thwarted by a treacherous stream swollen with spring melt, and he must retreat back to the bus. In a desperate effort to survive, he resorts to foraging but tragically mistakes a harmful plant for an edible one, falling gravely ill.
In his waning moments, McCandless continues to document his thoughts and reminisces about his family. He pens a poignant farewell to the world and succumbs to his fate, crawling into his sleeping bag one last time. Two weeks later, a group of moose hunters discover his lifeless body. Shortly thereafter, Carine retrieves her brother's ashes, carrying them back to Virginia in her backpack, a testament to the tragic conclusion of his quest for freedom and understanding.
