As Marianne refused any intimacy with the Misses Steele, they turned to Elinor. Lucy, especially, sought her out, and Elinor frequently found her clever and agreeable, but she also found her "ignorant and illiterate" through lack of education, and wanting in "delicacy, . . . rectitude, and integrity of mind."
One day while walking with Elinor, Lucy persisted in asking her opinion of Mrs. Ferrars, Edward's mother. She hinted that she would soon be "very intimately connected" with the family, and to Elinor's amazement, she confided that she had been secretly engaged to Edward for four years: "He was four years with my uncle, who lives at Longstaple, near Plymouth. It was there our acquaintance begun." She showed Elinor a miniature of Edward which she carried in her pocket and spoke of the sufferings she had endured on his behalf: "Everything in such suspense and uncertainty, and seeing him so seldom."
Elinor desperately hoped that Lucy was lying, but all hope vanished when Lucy showed her a letter from Edward and told her that she had given him a lock of her hair, set in a ring.
Ironically, the vulgar Lucy becomes Elinor's rival. She is forced to listen to Lucy's confidences about him and is abashed to realize that the lock of hair in Edward's ring, which she fondly believed to be her own, is in reality Lucy's.
Note how often Austen uses letters to give a turn to the plot. In an earlier chapter, Colonel Brandon "changes colour" and leaves mysteriously when he receives a letter. In this chapter, Lucy shows Elinor a letter which convinces her that Lucy is speaking the truth about her engagement to Edward.