Xand van Tulleken and historian Tracy Borman examine the plot to kill James I by blowing up the House of Lords when the king would be present for the State Opening of Parliament. They follow Robert Catesby and his co-conspirators as they assemble their gang to carry out the attack, revealing just how dangerous it was to smuggle two and a half tons of gunpowder beneath the House of Lords, and show how the assassination of so many people in Parliament was meant to be the beginning of an audacious coup to take over the country.