Christopher is an orphan boy who works for Mr. Absalom, an engineer who creates mechanicals, a 1930s version of robots. These mechanicals are not perfect, and are all children, according to the English laws of the time. The group ekes out an existence, doing work and repairs for income. Mr. Absalom even tries to sell one of his works, Jack, but that falls through. When Christopher is injured, the truth is revealed-- he is not human, but mechanical like his friends. Not only that, but he is of such high quality that it is suspected he is the work of Philip Cormier, an engineer who produced excellent work but who fell into disrepute when his work on war machines with Blake went badly wrong. The inspectors come and remove Christopher to the care of Blake's son, and Mr. Absalom's mechanicals are ordered to be deconstructed. Instead, they run away to find Cormier, who can claim Christopher as his own work. They find Cormier in a community of damaged mechanicals, and manage to convince him to help. This involves breaking into the agency that oversees mechanicals and stealing the Diviner, a device that can locate separate units. They track Christopher down, but Blake's son wants to continue his father's work, which included "ensouling" mechanicals, which is illegal. There is an epic fight between Blake's creations and Absalom's group of friends, who are sorely outnumbered. With determination, grit, and Cormier's help, can they win their freedom?