Greenock, near Glasgow, the present. Liam and Pinball, two teenagers from the streets, eke an existence by selling contraband cigarettes in a local pub. With his granddad, Rab, and stepfather, Stan, Liam visits his heroin-addicted mum, Jean, in prison after taking the rap for Stans' drug-dealing. Knowing they will be searched, Stan instructs Liam to hide Jean's drugs in his mouth.

In the visiting room, Liam refuses to hand over the drugs, to the annoyance of his family. Outside, Stan assaults him. Returning home, Liam discovers his possessions have been thrown out into the garden, and he is ejected from the family house.

Accompanied by his friend Pinball, the two lads visit Liam's sister Chantelle and her young son. She offers to let him stay with her. On a joyride with Pinball, Liam notices a caravan by the estuary, and begins to dream of a future there with his mum when she is released from prison.

Overlooking the housing estate with Pinball, Liam sees Stan hiding his drug stash in a garden, and decides to steal it. That night, the boys acquire the score and proceed to sell it on the streets. Eventually, they have enough cash to put down a deposit and first installment on the caravan.

Liam visits his mum again in prison, informing her of his plans when she is released - on his sixteenth birthday. He shows her photos of the caravan he has bought and registered in her name. On the streets, Liam is attacked by a group of rival dealers; Chantelle nurses his wounds.

Liam and Pinball are kidnapped on the street and taken to meet Tony, the gang leader who controls the drug trade in the area. Liam is later provided an opportunity to initiate himself into the criminal organisation, by committing murder. Although he is not obliged to go through with the act, Liam shows enough 'bottle' to please Tony.

Liam and Chantelle, looking forward to a picnic in the caravan, arrive to discover it has been burned down. Suspecting Stan, Liam smashes a window of his house. Jealous of Liam's new underworld connections, Pinball steals Tony's car and ram raids his health club.

Tony offers Liam employment as a drug runner and a modern apartment if he deals with Pinball. Pinball tells Liam it was he who burnt down the caravan and, as an act of self-punishment, proceeds to cut his own face with a penknife . Liam works as part of a team, delivering drugs and using Tony's pizza delivery company as a front.

Liam greets his mum as she is released from rehabilitation, taking her to view the modern apartment he has been given by Tony. The morning after a welcome home party, Liam is distressed to discover that his mum has gone. He finds her at Stan's house. An argument breaks out and Liam stabs Stan.

Desperate and alone, Liam walks on the beach, where he receives a phone call from Chantelle, who declares her love for him.