There are two related "monsters" that the characters in Ivanhoe have to defeat: family resentment and Norman-on-Saxon violence. The first couple chapters outline what our hero, Ivanhoe, has to face: bullying Normans, rebellious Prince John, and a father who hates him for following Norman King Richard I on a Crusade to Palestine. The rest of the plot will be about dealing with these challenges.
At first, it looks like Ivanhoe is going to have no trouble overcoming the Normans who are making life hell for the local Saxons, including his father, Cedric of Rotherwood. After all, Ivanhoe practically breezes through the tournament at Ashby-de-la-Zouche, defeating Brian de Bois-Guilbert without too much trouble. Surely his father will forgive him now that he is clearly fighting for English rights against his father's Norman foes.
Ivanhoe ends the tournament with an injury that keeps him out of the action for the next twenty-odd chapters. Rebecca carries him off to heal, which would seem to be a good thing (she's really skilled at medicine), but actually it only increases Cedric's resentment of his son. Cedric assumes that Ivanhoe has been taken in by the Normans for treatment. He thinks Ivanhoe's sudden disappearance is another sign of his lack of gratitude for his father. Suddenly, overcoming both the Normans and Cedric's rage doesn't seem so easy after all.
Of course, everything gets worse: Ivanhoe is too weak to prevent Bois-Guilbert from carrying off Rebecca during the battle at Torquilstone. Now that she is in Templar hands, she has a very good chance of getting burned at the stake for witchcraft. If she is, it will be at least partly Ivanhoe's fault, since she's only involved in this whole disaster thanks to her efforts to save him from his injuries at the tournament. Meanwhile, King Richard is taking his own sweet time about removing his disguise, taking his throne back, and putting Prince John in his place. Richard's slowness only delays the resolution of the Norman-vs.-Saxons plot line.
Finally Ivanhoe overcomes his challenges. He rides to Rebecca's rescue just in time. Bois-Guilbert, the worst of the bullying Norman knights, dies suddenly during his duel with Ivanhoe. King Richard tells Cedric his true identity and asks Cedric to forgive Ivanhoe. Cedric agrees that King Richard isn't so bad for a Norman, and he and Ivanhoe reconcile. So the Normans back off the Saxons and the family drama between Cedric and Ivanhoe is resolved. All is (mostly) right with the world – though we still think Rebecca gets a raw deal. For more on the loose ends left at the end of Ivanhoe, check out "What's Up With the Ending?"