The opening text states that, from 1965 to 1973, photographer Danny Lyon (Mike Faist) documented his time with a motorcycle gang and wrote a book about his experiences. This film is based off of that book.
Chicago, 1965 – Two men approach Benny Cross (Austin Butler), member of the Vandals Motorcycle Club, and demand that he take his jacket off since they don’t like him wearing those colors there. Benny tells them that they will have to kill him to get the jacket off him. One of the men hits Benny with a stool before throwing him outside. As they try to continue antagonizing him, Benny slashes one of the men’s face with a shovel, while the other man whacks Benny in the back of the head with his own shovel.
At a laundromat, Danny is beginning his interviews by starting with Benny’s wife, Kathy Bauer (Jodie Comer). She tells Danny about how she first arrived in town and was at a party where she met Benny and the other Vandals, led by Johnny (Tom Hardy). The other bikers harass Kathy but she is told by Johnny that Benny likes her. She later goes for a ride on the back of Benny’s motorcycle while the other Vandals tease.
Benny brings Kathy back home, where her husband is sitting outside. He is none too happy to see Kathy returning with a biker. Benny ends up standing across the street from Kathy’s house all night going into the morning, which enrages her husband after he returns from work to the point that he gets fed up and leaves Kathy for good. Five weeks later, Kathy marries Benny.
Danny learns about the other members of the Vandals, including Brucie (Damon Herriman), Zipco (Michael Shannon), Cole (Boyd Holbrook), Wahoo (Beau Knapp), Corky (Karl Glusman), and Cockroach (Emory Cohen). Johnny comes up with the idea to develop a bigger motorcycle club rather than just the small group that sits around talking about riding. Meanwhile, a young man, only credited as “The Kid” (Toby Wallace), witnesses the Vandals riding and aspires to join them to escape his abusive home life when his mother kicks him out after he nearly kills his violent father.
One Vandal, Big Jack (Happy Anderson), comes to Johnny with the proposition that other biker friends of theirs open up a new chapter of the Vandals in Milwaukee. Johnny says no but Big Jack steps up to challenge him. Johnny asks “fists or knives”, Big Jack chooses fists. The two have a brawl outside where Big Jack almost gets the upper hand on Johnny, only for the latter to go dirty and get Big Jack on his knees after breaking his finger. Johnny then says he was always going to let them open a new chapter, but he needed to demonstrate his authority.
Benny is shown as deeply loyal to Johnny. When a rival biker group goes to antagonize Johnny, Benny immediately jumps in to hit the other gang’s leader, leading to a brawl between the bikers.
The rest of the film jumps between Danny’s last interview with Kathy in 1973 to earlier points in the gang’s history. Kathy recounts to Danny how Benny rarely showed emotion, and the one time she came close to seeing him cry was the day he fought the men at the bar. After taking the shovel to the head, the attacker brought the shovel down on Benny’s foot, nearly severing it and making him fear he would never ride again.
Johnny and the Vandals arrive at the bar and threaten the bar owner to give up the names and addresses of the men that attacked Benny. After the bar closes, Johnny orders the Vandals to burn it to the ground, while onlookers later watch at night in fear of the Vandals.
The Kid and some of his buddies show up at the Vandals’ bar to get Johnny to let them join the gang. Johnny refuses, and The Kid makes an attempt to stab Johnny, but he hits The Kid twice to get him to go away. Later, the Vandals gather around the park and are met by another biker, Funny Sonny (Norman Reedus). He claims he was sent by his gang to go after Cole and beat the shit out of him since he deserted his gang, but Sonny has taken a liking to the Vandals and decides to join them.
Kathy recounts how Johnny started making the gang more violent compared to how it started out. She tells Danny how Cockroach wanted to turn in his colors to start a job as a motorcycle cop. Three younger Vandals attack him as a result, and Cockroach comes to Johnny with this, fearing for his life. Johnny later brings Benny to find Cockroach, with Johnny ordering Benny to bring a pistol. They go to Cockroach’s house, where Johnny shoots him in the leg and orders him to get lost. Benny then expresses disapproval of Johnny’s actions.
The Vandals later throw a party. Kathy sees a woman in a red dress and comments that she likes the dress. Benny and one of his buddies swipes the dress off the woman as she has sex with two guys, and they have Kathy wear it. She likes how it looks on her, but after Benny disappears, a few other bikers see Kathy and attempt to forcefully pull her upstairs before Johnny intervenes. One of the men defends himself by saying “the woman in the red dress” was giving everybody a turn, not knowing it wasn’t Kathy. A traumatized Kathy later chastises Benny for not being around when this happened.
Later on, The Kid returns to the bar to challenge Johnny for his leadership. Johnny asks “fists or knives”, and The Kid responds with knives. Johnny gives him a time and place to meet. Before going to the location, Johnny stops by Benny and Kathy’s home one last time, but Benny is not home. Johnny goes to the parking lot with other Vandals, but The Kid shoots Johnny once in the chest, instantly killing him.
Kathy tells Danny that with Johnny gone, The Kid took over the Vandals and perverted it into a more violent criminal organization, running drugs and prostitutes, as well as killing rival bikers. After Benny learned of Johnny’s death, he cried in Kathy’s arms. She tells Danny what happened to some of the other Vandals – Wahoo and Corky turned in their colors and left, Cole died in an accident, and Cockroach fulfilled his dream of being a motorcycle cop. Kathy states that Benny never rode again after they moved away from Chicago. She sees Benny outside with a friend, while he reminisces about biking and the sound of the motors running. Benny then looks up at Kathy and smiles at her.
