Guy the Foudling, left on the steps of carpenter Simon Grandely's house on a stormy night, often clashes with his fellow apprentice Dick Hatherden, and the third of them, Will Lightmore usually able to break them apart. At the same time as their relations take a dire turn, a set of mysteries appear around them: who is Colonel Halsted who asks for so many strange jobs? Where do these strange men come from who appear to use secret passages around Grandley's home? And why is Grandley himself becoming more secretive of his personal business? This story takes place amongst the anti-Catholic Gordon Riots of 1780.