Plot
Tom Heath, a withdrawn teenager living in South London with his single mother Mary, dreams of becoming a rock musician. At school he is bullied by classmates, especially his rival Damien, and retreats into fantasies of stardom while hiding his passion from Mary, who disapproves of music due to Tom's father, Chris's, failed career as a musician. Chris shows little interest in Tom and eventually abandons the family, leaving Tom devastated. Struggling with isolation, Tom also has scars from past self-harm, which he has tried to overcome through playing the guitar.
When a new tenant moves into their council flat, Tom discovers he is Max Stone, an American former rock guitarist who vanished years earlier after his young son drowned and he was charged with tax fraud. Presumed dead, Max lives in hiding, blasting music day and night. Fascinated, Tom begs him for guitar lessons. Max angrily refuses, but Tom blackmails him by threatening to expose his identity. Though initially reluctant, Max eventually agrees, and the two begin an uneasy mentorship.
As Tom learns under Max's guidance, the pair grow closer, with Max slowly warming to the boy. Mary, unaware of their lessons, gradually begins to get along with Max. When she discovers he has been secretly mentoring Tom, she feels betrayed and lashes out, accusing Max of being unfit to guide a child. Shaken by her words and haunted by guilt over his own son's death, Max leaves a letter for Tom and withdraws from his life. Depressed, Tom relapses and self-harms.
Tom is approached by Felix, a girl from Damien's band whom he admires. She is impressed by a video of Tom playing with Max, and invites him to contribute as a songwriter. Tom agrees, but Damien steals his work and threatens to reveal Max's survival to the authorities. Feeling hopeless, Tom contemplates suicide on the roof of his building, but is stopped by Max, who urges him to channel his pain into music instead.
Determined, Tom enters the local battle of the bands competition. Initially paralysed by stage fright, he is supported by Felix, and together they begin to perform. Midway through, Max makes a surprise appearance, clean-shaven and revitalised, and joins Tom on stage. Their duet wins over the crowd, and videos of the performance quickly spread online.
Police arrive and arrest Max. Though Tom begs him to flee, Max chooses to face justice and is sentenced to three years in prison for tax fraud. Tom continues to visit him with Mary, and he begins a romantic relationship with Felix. The viral video of Tom and Max prompts fans to crowdfund £500,000, launching Tom into fame. Years later, Max is released from prison. Tom, now a confident young musician, reunites with him, and the two perform together, fulfilling Tom's dream of becoming a rock star.
