This poem is about the mysterious meeting of Christabel and Geraldine, and the mysterious effect Geraldine has on both Christabel and Christabel's father.
"Christabel" opens by establishing an eerie setting that contributes to the tone. The night is chilly, and thin gray clouds cover the sky in the middle of the night. Owls are so loud that they have awakened the roosters, and the moon looks dull although it is full.
Christabel, a lovely lady, decides to go out in the middle of the night to pray in the forest. She kneels down beside a huge oak to silently offer her prayers for the "weal of her lover" when she suddenly spots a "damsel bright" who is dressed in a white robe. This woman, who identifies herself as Geraldine, is described with words that convey a mysterious presence. She has "blue-veined feet" and gems that are "entangled" in her hair which "wildly" glitter in the moonlight. Her appearance is strange, and she asks Christabel to take pity on her because she is so weary. Christabel asks Geraldine why she is lurking in these woods, and Geraldine tells her about five warriors who "seized" her the previous morning.
Christabel reaches out to comfort Geraldine and then decides to walk her to her own home. The two enter Christabel's chamber, where Christabel offers Geraldine some wine. Christabel shares that her own mother died when she was born. Both women undress and then get into Christabel's bed.
The next morning, Sir Leoline listens for the bells which, by law, have been rung each morning since his wife died, as a means of honoring her.
Inside Christabel's chamber, the women awaken. Christabel believes that Geraldine is even more beautiful than she was beneath the oak tree. The details of their time together that night are not given, but Christabel does declare that she has "sinn'd" and prays for Christ to "wash away [the] sins" she committed during the night, which she can't seem to recall that morning.
Christabel takes Geraldine to meet Christabel's father. Sir Leoline realizes that Geraldine is the daughter of Lord Roland de Vaux, who was a close friend of his when they were young. Following a disagreement, however, the two men never spoke to each other again. With tears in his eyes, Sir Leoline embraces Geraldine, proclaiming that he regrets ever speaking in "fierce disdain" against her father. Geraldine falls to the ground, swearing that Sir Leoline's sweet words are too gracious.
Meanwhile, Christabel begins to notice Geraldine's menacing features. Geraldine's eyes shrink to look like those of a serpent; Christabel begins to stumble and shudder as Geraldine's serpent eyes look "wildly" upon Sir Leoline. Christabel isn't able to convey the truth of what she has seen and is only able to beg her father to send Geraldine away. Sir Leoline is enraged by his daughter's request and tells her that she has dishonored him. The poem ends with Sir Leoline turning from his daughter and leading Geraldine away.