In an alternative England of the 1930s, a young orphan named Christopher lives with the devious, disgraced, and unlicensed engineer Gregory Absalom, who makes his living scamming the vulnerable and downtrodden with his life-like robotic inventions. Absalom makes mechanical children, and sells them to parents who lost their own children in the recent War, never telling them that they're mechanical. These constructed children have no choice but to help him in his unlawful practice, and Christopher is forced to assist as well. 

But despite Absalom's awfulness, Christopher enjoys the days he spends playing with his gang of tight-knit mechanical-child friends. Their lives pass in a quiet sort of run-down, monotonous joy, until the fateful day when Christopher is hit by a car while trying to rescue one of his pals. In an instant, the friends' entire world is turned on its head. Christopher, it turns out, is not a boy after all, but a robot. A highly-illegal, incredibly advanced robot. 

Shortly after this discovery, Christopher is abducted by government agents, led by the villainous engineer, Richard Blake. Blake is intent on discovering the secrets of Christopher's technology, even if it means tearing him apart in the process, and it's up to Christopher's robotic friends to rescue him before it's too late. 

Tin is a heart-rending and magical story of loyalty, friendship, courage, and what it means to be human.