It's 1992 and college graduate Christopher McCandless (EMILE HIRSCH) has achieved his life goal of arriving and then living by himself in the Alaskan wilderness. Setting up camp in an abandoned bus, he tries to survive there, all while reflecting on the journey that led to that point.
Two years earlier, he's a graduate of Emory University, adored by his younger teen sister Carine (JENA MALONE). Yet, his idealism clashes with his conservative father, Walt (WILLIAM HURT) whose marriage to Billie (MARCIA GAY HARDEN) is on shaky ground.
Disillusioned with who and what he's supposed to be, Chris simply drops out from society, destroying all forms of identification and adopting the name Alexander Supertramp. He then sets out across the country, taking odd jobs here and there -- such as working for farmer and satellite receiver box bootlegger Wayne (VINCE VAUGHN) -- while meeting an array of interesting people, such as aged hippies Rainey (BRIAN DIERKER) and Jan (CATHERINE KEENER) who briefly and unofficially adopt him.
He later crosses paths with them again, which is when he meets young singer Tracy (KRISTEN STEWART) who takes an instant liking to him. Yet, he has no intent on settling down in one place, meaning after he spends some time with her and then widower Ron Franz (HAL HOLBROOK), he sets off once again, intent on making it to Alaska, and living a life that's solely his.