The story opens with 14-year-old Ponyboy walking home from the movies and thinking about life. He knows he shouldn't be walking home alone, because his gang of poor kids known as Greasers frequently gets beat up by the rich kids, knows as Socs (pronounced "so-sh" or "so-shiz" when plural). He didn't want to take anyone with him though, because no one else in the gang really appreciates stories the way he does. Sure enough, Ponyboy gets jumped by a group of Socs on the way home. Luckily, the members of his gang see what's happening and run in to help. Now we meet them: Pony's older brother Sodapop and oldest brother (and father figure, since the boys are orphans), Darry. As for the rest, we have Two-Bit the joker of the group; Dally, the rough one from New York, Steve, Sodapop's best friend; and Johnny, the second youngest living in perpetual fear of beatings from Socs and his parents.
The next night, Ponyboy, Johnny, and Dallas go to the drive-in movies. Dallas decides to harass the two Soc girls sitting in front of them, until Johnny tells him to stop. Dally gets mad and Pony notes that Dally would have hit anyone else, but Johnny is the gang's pet, so Dally storms off instead. The girls, Cherry and Marcia, invite Johnny and Pony to sit with them. Two-Bit shows up and him and Marcia crack each other up with jokes. Meanwhile Pony and Cherry seem to have a lot in common and Pony opens up to her about Johnny's terrible beating by the Socs, in which he almost died.
The boys decide to walk the girls to Two-Bits to drive them home, since they have ditched their drunk Soc boyfriends. The drunk boyfriends show up in a car with their friends, though, and the girls leave with them to avoid a fight. Pony and Johnny lie down in a lot and fall asleep talking. When Pony wakes up at 2 AM, he knows Darry will be furious (Darry takes his job of makeshift father very seriously) and so he runs home. He and Darry get in a huge fight about Pony's lack of street smarts and poor decisions and Darry ends up slapping Pony. Pony runs back out of the house and grabs Johnny to tell him they're running away.
Pony knows he just needs to cool down, though, so they wander around the park for a bit. That's when the Socs come back, ready for revenge on Pony and Johnny "taking their girls." When one of them tries to drown Pony in the fountain, Johnny pulls out the switchblade he's carried since his first attack and stabs Bob (Cherry's boyfriend). Horrified, the boys run to find Dally to help them out of this mess.
Dally hooks them up with some cash and a gun and gets them on a train to the countryside, telling them to make for an abandoned church to hide. They do, reading from Gone with the Wind to pass the time and cutting their long hair to hide their identities. On the 5th day, Dally comes to visit and they go out for burgers. When they come back, the church is on fire from one of their cigarettes. Worse still, so children who were there on a field trip are trapped inside. Pony runs inside to help, with Johnny hot on his heels, and Dally running after telling them to not risk their lives for some kids.
All three of them end up in the hospital. Johnny is especially bad off, as a piece of flaming timber fell on his back. The timing is nearly perfect, as the Greasers and Socs have a big rumble planned for the next day. Johnny killing the Soc has had serious repercussions and this rumble is meant to decide things once and for all. Pony and Dally get out and fight and the Greasers win. Dally grabs Pony and takes him to tell Johnny.
While they are there, Johnny dies from his injuries. Dally runs off and Pony hitches a ride home. The rest of the gang is waiting and they hear that Dally has robbed a store. The gang witnesses him pull out a gun so the cops will shoot him.
There is a trial for Ponyboy, to decide if he can keep living with his brothers or will need to go into foster care. It's decided that he can stay, but he goes through life in a daze, losing his good grades and sense of purpose. That is, until his English teacher assigns him a story to write from his heart. Thinking back on the events of the year, Pony starts writing the story of what has happened to him.