For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
King Uther conceives a son with Igrayne, a boy named Arthur – his boy goes on to pull the sword from the stone and claim the throne of England. Impressive, no? Arthur marries Gwenyvere and establishes a Round Table fellowship of 150 knights. We're all set for intrigue, romance, and of course, adventure.
Act II
Arthur's knights win great glory on quests and on the battlefield, and Arthur is reputed to be the greatest king that's ever lived. However, one of Arthur's knights, Launcelot, is in love with Arthur's wife, which makes things a bit difficult. And the unity of the Round Table is threatened by an ongoing feud between the families of King Lot and King Pellynore. Things come to a head when the Lothian faction, headed by Aggravayne and Mordred, surprise Launcelot in the Queen's bedroom, forcing Arthur to convict her of treason and sentence her to be burned at the stake. Talk about marriage woes.
Act III
Launcelot rescues Gwenyvere from burning, accidentally killing two Lothian knights, Gareth and Gaheris, in the process. This prompts Gawain to seek vengeance for their deaths by encouraging Arthur to go to war with Launcelot, which he does. The power vacuum this opens enables Mordred to seize power in England, and Arthur loses his life fighting to regain it. Gwenyvere and Launcelot repent for what they have done and enter the religious life.