Robin, Earl of Huntingdon, returns to Locksley from fighting with King Richard in the Crusades, but England is not as he left it and all attempts to resume his former life are foiled by the Sheriff of Nottingham.
Robin captures a tax inspector and plots to heist the year's taxes, but a surprise is in store for both him and the sheriff; Marian makes her own preparations after a row with her father, and Gisbourne makes his intentions clear.
Allan A'Dale's brother comes to Locksley and keeps putting his foot wrong; meanwhile at Nottingham the Sheriff is convinced there's a spy leaking info to Robin, but the trap Gisbourne sets has far-reaching consequences.
When Gisborne betrays a friend to obtain Greek Powder for the Sheriff, Robin scrambles to find the recipe and stash of powder before the Sheriff turns it against him. Elsewhere, Much is unexpectedly promoted, and Marian puts her trust in the wrong man.
The glorious news spreads that King Richard is returning to England. For most it hails a return to the good old days, but for Will and Allan it means a return to their lacklustre former lives - and for Robin and Marian it means her impending marriage to Guy of Gisborne. Robin is desperate to find evidence convicting Gisborne of his crimes, while Marian sets out on one last mission as the Nightwatchman. But tragedy strikes and as the Sheriff and his men surround Robin and the gang it seems that Marian and Robin will be separated forever- if not by Gisborne and the ...
Robin cannot come to terms with losing Marian. He refuses to help Edward in confronting the King and abandons Much and the gang: his world has fallen apart. There is no point in being Robin Hood anymore. But all is not what it seems and the discovery of a terrible secret will spur Robin back into action and see the Sheriff and Gisborne defeated before the day is out.
In his first mission since discovering the devastating truth about operation Shah Mat, Robin launches an abortive raid on Nottingham Castle's new Strong Room. The Sheriff has stored all his Shah Mat funding in the medieval Fort Knox, but, before the Black Knights arrive to divide up the silver, he's preparing a final big deposit.
When a group of boys accidentally stumble on Gisborne's weapons-testing site, all but one is taken prisoner. The resourceful escapee, Daniel, is able to elude Gisborne's men and runs to Robin to raise the alarm. Robin is horrified to discover that Gisborne has developed an indestructible new suit of armour, made of special Damascus steel - an army wearing this armour would easily defeat King Richard and must be stopped!
The Sheriff and his sinister scientist, Joseph, are testing a chemical weapon on a street in Nottingham Town and blaming the ill effects on the Pestilence. But Dan Scarlett (Sean Murray), who is in town to visit his son Will, knows it is not the pestilence at all.
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 (John Hopkins) 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. With his dying breath, he tells Robin that the King needs him to return to fight in the Holy Land, and utters the word "Lardner".
Tormented by Robin Hood, The Sheriff sleepwalks straight into Sherwood Forest. Unfortunately, he goes missing on the very day that Prince John's messenger, Jasper, arrives to check all is well in Nottingham. By the time Gisborne raises the alarm, Prince John's private army is already on its way, ready to raze Nottingham at sunset. Drastic action is called for, so, while keeping up appearances with Jasper, Gisborne and Marian secretly task Robin with tracking down the Sheriff in the forest.
The Sheriff has turned Locksley into a garrison town, throwing its people out to make room for an army of vicious mercenaries. As Robin and the outlaws formulate a response plan to stop them, they are intercepted by three burly King's Guards, led by the fearsome Legrand who brings a vital message from King Richard.
Robin and the Outlaws arrive at a barn for Robin's birthday party, only to find that they are surrounded by The Sheriff's mercenaries and will not be let out alive. The Outlaws share their secrets with one another while the traitor, Allan A Dale, realizes that The Sheriff and Gisborne are heading to the Holy Land to kill the King. Fearless Marian takes it upon herself to stop The Sheriff in his tracks, while Allan must choose his allegiance.
Robin and the Outlaws, The Sheriff, Gisborne and Marian are now in the Holy Land. Robin warns the King of the impending threat to his life, but The Sheriff's cunning has prevailed and, instead of a heroes' welcome, Robin and the Outlaws are treated as traitors. Marian makes a final attempt to redeem Gisborne - if he kills The Sheriff, he will have everything he wants, including her.