The Sheriff and his sinister scientist, Joseph (pretending to be the Nightwatchman), test a poison, blaming the ill effects on the pestilence.

A horrified Robin realises that his plan to capture the Sheriff's spy, Henry of Lewes, has failed because he has a traitor in his gang. Fearing for Marian's safety in the castle, Robin sets about rooting out the turncoat. His only clue is supplied by Marian: the spy's meeting place is located at the Trip To Jerusalem Inn, where the traitor outlaw sells his secrets to Gisborne.

The Sheriff's Black Knights gather at the castle to attend a feast and declare their allegiance to Prince John by signing the Great Pact of Nottingham. With the outlaws disguised as entertainers, Robin infiltrates the castle to join forces with the only man who can stop them: former Sheriff Edward's old ally and Black Knight, the Sheriff of Winchester. Winchester's territory is key to the Sheriff's Shah Mat plan that will apprehend a homecoming King Richard at the southern ports.

Robin is determined to get hold of the Great Pact of Nottingham, written proof of the Sheriff's treason. So when lovelorn Knight John of York and his chest of silver pass by Robin and the gang, and the Knight begs the outlaws to take pity on him and save his girl, Robin formulates a plan.

Marian wakes up in Sherwood Forest on the first day of the rest of her life as an outlaw with Robin and his gang. Surprising everyone with a new energy and recklessness, however, she jeopardises the gang's mission to bring aid to Clun Village after it's ransacked by the Sheriff's men.

A mortally wounded, one-legged messenger from King Richard flees Locksley Manor pursued by Gisborne's men and ends up in the arms of Robin. In his dying breath, he tells Robin that the King needs him to return to fight in the Holy Land, and utters the word "Lardner". The Sheriff is furious that the messenger got away, especially now that he and Gisborne are also on the hunt for Lardner, having received a prediction from a fortune-telling Fool that the "ring of Lardner" spells trouble.

Prince John's army is summoned to raze Nottingham to the ground at sunset. Gisborne risks his life standing by Marian as they fight to save the townsfolk from oblivion.

The King's guard Legrand arrives with a vital mission for Robin. Robin joins the quest to unravel the coded clues leading to the mysterious Thesaurus Patriae.

The gang are captured by the Sheriff's mercenaries. Allan a Dale realises that the Sheriff and Gisborne intend to kill the King.

The Sheriff, Gisborne and Marian are in the Holy Land. It is up to Robin to save the King's life as the battle for England is on.