In the film
It is in this place where King Richard prepares to leave with the Earl of Huntingdon for the Crusade while his greedy younger brother, Prince John assumes the throne and the Earl's daughter, Maid Marian is left in the King and Prince's mother, Queen Eleanor's care. Queen Eleanor can be seen wishing her eldest son good luck on his Crusade and the Archbishop of Canterbury is also seen giving a blessing to the King, the Earl, and everyone else. After King Richard's departure, it is there where Prince John appoints a man to be his new Sheriff of Nottingham.
A few days later, it is there where the Sheriff punishes two men: Scathelock and Will Stutely for breaking Prince John's laws until they are saved by outlaws known as Merrie Men who follow their leader, Robin Hood. On that day, after the Prince returns to the castle to find the people revolting against them, the Prince can be seen scolding his Sheriff while his Sheriff promises to put an end to Robin Hood and his men the next day.
Two years later, after King Richard's Crusade has ended in failure and King Richard finds himself imprisoned in Austria to be held for a ransom of 100,000 marks, it is at the castle where the Queen Mother, the Archbishop, and Maid Marian go to consult Prince John when they find out that he hasn't raised and refused to contribute to the fourth of the ransom. At the castle, Prince John lies to his mother; claiming he never knew or heard of his own brother's capture and ransom from his mother's messengers, whom he also claims they never reached him as well.
Using his wit, he decides to hold a donation tomorrow at Nottingham Square. Still, the Archbishop and his mother suspect he's up to something. Prince John gives them an excuse by telling them that he's been busy forming an army of foresters against Robin Hood and his outlaws. Having known Robin Hood all her life, Maid Marian refuses to believe his story (including the story of how his father was killed) and tries to persuade the Queen to allow her to find Robin and prove her his loyalty to their King. But the Queen refuses since she is her responsibility and Prince John continues to mock and rebuff Robin Hood.
The next day, the donation takes place and the King's deliverance is assured thanks to Robin Hood and his men, who also contribute with their own through Maid Marian, who deliberately disobeyed the Queen the other day for a good cause. At night, refusing to give up all his tax money and to allow his brother to return home safely, Prince John plans to disguise his men as Robin Hood's outlaws to steal his money back tomorrow while the Queen and the Archbishop are conveying the ransom through Sherwood Forest. Knowing Maid Marian has been fraternizing with the outlaws and could see through their deception, thus, jeopardize their plan, Prince John and the Sheriff have her imprisoned in the castle's dungeon and make his mother believe she is with Robin Hood.
After the plan fails to succeed, at night, Robin and his men (disguised as Prince John's guards) return to the castle and force Prince John and the Sheriff at knife point to take them to Maid Marian and free her. Finally, Prince John is thrown in Maid Marian's place in the dungeon by Little John while the others handle the Sheriff, who later meets his demise when trying to finish off Robin Hood once and for all.