Ivanhoe was a Saxon knight who, like King Richard, returned from the Holy Lands to oppose Prince John and abuse of the Saxons. The action centers around three events: a tournament, abduction, trial.
In the tournament Ivanhoe and the Black Knight (King Richard in disguise) ultimately vanquish the Normans.
In a mix-up reminiscent of Shakespearean comedy, some Norman nobles abduct a Saxon princess so another Norman noble can rescue her and win her affection. Much goes wrong with this plan, including the accidental abduction of the wounded Ivanhoe, a Jewish father and his beautiful daughter. One of the Normans falls in love with the Jewess, and the castle is ultimately burned down when Robin Hood, King Richard (in disguise), and company rescue the various captives.
Finally, the Jewess is accused of being a witch, but she is ultimately defended by Ivanhoe in a trial by combat.
The Jewess and her father have bigger roles in the story than either of the three heros: Ivanhoe, King Richard or Robin Hood.
I found the book very difficult to read. Sir Walter Scott was a contemporary of Jane Austen who wrote in a much more readable style. Here is a not atypical sentence (seven commas!):
Without attempting to conceal her avowed preference of Wilfred of Ivanhoe, she declared that, were that favored knight out of question, she would rather take refuge in a convent than share a throne with Athelstance, whom, having always despised, she now began, on account of the trouble she received on his account, thoroughly to detest.Interestingly, the book opens with the observation, repeated in many places since, that farm animals have Anglo-Saxon while food have Norman-French names (e.g. Cattle/Beef, Swine/Pork, Sheep/Mutton, Chicken/Poultry).