On the 5th of November 1605, a small group of radical Catholic conspirators, including Guy Fawkes, came within hours of blowing up the Houses of Parliament. In a cellar deep below London's Parliament, Guy Fawkes prepared to light the fuse on the deadly attack. They aimed to assassinate the Protestant King James I and destroy his government in an attempt to restore England to the Catholic faith. Had it not been stopped, this one moment of violence could have changed the history of Britain entirely.

The Gunpowder Plot was foiled, but its remembrance was written into law, and Guy Fawkes Night is still celebrated on the 5th of November. Lucy Worsley investigates what drove this group of men to attempt such an audacious act.

She revisits key moments and locations in the plotter's lives: the city of York, home to Fawkes and other plotters, and Ashby Manor, Northamptonshire, home of mastermind Robert Catesby. She delves into the motivations and mindsets of the Catholic plotters, searching for evidence in their childhoods, the rooms where they secretly met, and where Guy Fawkes finally faced his interrogators. She then consults experts who help contribute to the uncovering of this extraordinary moment in history.