In the sweltering London summer of 1666, Samuel Pepys curries favor with King Charles II, whose chief of intelligence suspects a plot against the throne. Fire breaks out in the Pudding Lane bakery of widower Thomas Farriner, father of two daughters.

Thomas flees the burning city with his family. Shocked at the speed of the inferno’s spread, Pepys calls on the king to address the mayor’s failing efforts. Thomas’ sister-in-law, Sarah, is imprisoned in Newgate as her son searches for her.

Thomas returns to the fire to rescue Sarah and David. The king, angry that his own advisors overruled his orders to fight the fire, is informed that a Catholic plot to unseat him was allegedly masterminded by his brother, James.

As the fire creeps close to the gunpowder-filled Tower of London, King Charles finally takes action. Sarah is recaptured and presented to the king as the fire’s instigator. Thomas seeks Pepys’ help to influence the king in her favor.