Liam's mum is due to get out of prison in time for his 16th birthday. He's determined to free her from the grip of her drug-dealer boyfriend, but that's going to take money. And the only way to make money is for Liam to rub shoulders with local drug dealers himself.
Hands up if you believe Ken Loach films don't have scripts, that the actors just improvise dialogue as the camera rolls.
Granted, the authenticity of Loach's work is rooted in the performances of the non-professionals in his cast. But to think that somehow it all falls together without anything on the page is a misconception that was happily blown out of the water when Paul Laverty won the Best Screenplay award at this year's Cannes Film Festival.
Laverty's writing has given a distinctive voice to four of Loach's films in the past six years. His former career as a human rights lawyer in Nicaragua fuels the politics of Carla's Song and, indirectly, Bread And Roses.
His observation of the difficulties facing working-class communities in areas of high unemployment brings heart to the drama in My Name Is Joe and Sweet Sixteen.
Laverty is the perfect collaborator for Loach; his politics are just as passionate, but his eye for character is tender and true, which helps soften the polemic. That's why Loach is at his best with My Name Is Joe and Sweet Sixteen - the films aren't about issues, they're about people. To this end, Sweet Sixteen is raised high by a storming debut from Martin Compston. The Scottish teenager carries the movie like a veteran, drawing us right into the tragic heart of Liam's dilemma. He's a cheeky, dignified, loving boy who is caught in a no man's land between a child's sense of fun and an adult's sense of burdensome responsibility. Around him, Loach and Laverty paint an all-too-credible portrait of modern-day Britain, with whole communities trapped in a dead-end existence. Sure, they make points about economic realities and social hardship; but the real focus of their anger is the loss to humanity, the snuffing out of that spark of life burning inside Liam.
Perhaps the Liam-Pinball dynamic is a bit too like Trainspotting's Renton-Spud pairing, but Sweet Sixteen is a moving and accessible little brother for My Name Is Joe.