King James of Scotland travels south to take the throne at the invitation of Robert Cecil. Meanwhile, John Gerard, a Catholic priest who has dedicated his life to the destruction of the Protestant state that developed in Elizabeth's England has escaped and made contact with a splinter cell in the Catholic underground containing an extremist called Guy Fawkes who has a plan to blow up Parliament with the King inside.

Cecil hears about the gunpowder plot, but is unaware of when and how they will strike and his investigation is hampered, as he's also trying to manage King James who has a wildly ambitious idea of unifying Scotland and England in a new kingdom of Great Britain.