In 1964, we are introduced to Jimmy Cooper, a young London Mod who finds himself deeply disillusioned by his monotonous life, consisting of parental conflicts and an uninspiring job as a post-room boy at an advertising agency. To escape this reality, he resorts to amphetamines, party scenes, spirited scooter rides, and confrontations with the rival Rockers, accompanied by his close friends: Dave, Chalky, and Spider.
Things take a turn when the Rockers launch a violent attack on Spider, leading to a grim retaliatory incident targeting Kevin, who is a childhood friend of Jimmy and part of the rival gang. Grappling with his emotions, Jimmy participates initially but soon realizes the implications of his actions; disillusioned, he confronts his friends yet rides away on his scooter in frustration, revving it loudly as a form of protest.
The tensions between the two groups come to a head during a planned bank holiday weekend in the beach town of Brighton, a setting ripe for rivalry. Jimmy aspires to elevate his stature as a 'face' within the Mod scene and flirts with the idea of riding alongside Steph, a girl he harbors feelings for. However, she chooses Pete, a wealthy older Mod, over him.
In preparation for the trip, the group tries to score some recreational drugs from a London gangster, Harry North, but finds themselves cheated with counterfeit pills. In a fit of anger, they vandalize Harry’s car and resort to robbing a pharmacy, stocking up on their favored amphetamine tablets called "blues".
Once they arrive in Brighton, after an energizing early morning ride, Jimmy spots a striking scooterist, which he dubs Ace Face. In an effort to impress Steph, who has been left to fend for herself as her dance partner flirts with an American girl, Jimmy attempts to seize the spotlight by lunging into an impromptu dance routine. His efforts, however, land him in trouble when he gets ousted by the bouncers, and Steph ultimately dances with Ace Face instead.
As chaos unfolds, the group finds themselves in the middle of a violent skirmish. When the police swarm in to break up the brawl, Jimmy escapes down an alley with Steph, where their relationship culminates in a passionate encounter. However, their moment is short-lived as they're caught in the clash of rioters and police, leading to Jimmy’s arrest alongside the erratic Ace Face. Following a hefty fine that Ace Face cheekily offers to pay on the spot, Jimmy returns to London, where his descent into depression begins.
Back home, he faces turmoil as his mother kicks him out upon discovering his stash of amphetamines. He resigns from his job, squanders his severance on pills, and discovers that Steph is now dating Dave. After a brief confrontation with Dave, Jimmy finds his beloved Lambretta scooter wrecked due to a mishap with a postal van, pushing him further down into despair.
In desperation, he returns to Brighton, consuming larger quantities of pills and spiraling into an emotional crisis. Wandering through the remnants of his past encounters, he is taken aback to find Ace Face, his former idol, reduced to being a mere bellboy at the Grand Brighton Hotel. In a moment of recklessness, Jimmy steals Ace's Vespa scooter and heads towards Beachy Head, riding perilously close to the edge of the cliffs. For a moment, the joy of riding envelops him, but it quickly dissipates as he stares grimly at the ocean below. The film culminates in a poignant moment where Jimmy’s scooter tumbles over the cliff, echoing the opening scene of his solitary walk against a sunset—further emphasizing his tragic trajectory.
