LitCharts assigns a color and icon to each theme in The Once and Future King, which you can use to track the themes throughout the work.
Chivalry, Satire & Medieval Life
Fate (Time)
Quest and The Holy Grail
Might vs. Right
War
Summary
Analysis
Lancelot stays at the court for several weeks, but it is torturous to be around Guenever. Finally, he decides to venture out on his second quest. He sets out for the haunted castle of Corbin where King Pelles lives. But, on the way to Corbin, Lancelot comes across a village under the castle; all the people are lined along the streets to greet him; Lancelot feels different, as though colors are brighter and sounds clearer. He is told by the villagers there is a damsel locked up in a bath of boiling water—put there by Morgan Le Fay who was jealous of her beauty—and she can only be rescued by a knight. Lancelot enters the tower and comes across a room filled with steam. In the middle is a small, beautiful girl naked in a bath. Lancelot lifts her out of the bath and carries her from the tower. The damsel's name is Elaine and she is the daughter of King Pelles. Lancelot goes to stay with King Pelles and ends up staying for several weeks.
The damsel locked in the tower is a cliché from myth and one that White subverts. In myth, when a knight rescues a damsel, they typically fall in love with one another. However, here, Elaine will fall in love with Lancelot but he does not return that love.