Book 1, Part 15: Quixote and his reluctant squire ride up into the mountains after Cardenio. After a while, Sancho asks his master if he can return home, but is denied. Next, Quixote admits that he's mad, though he seems to take pride in the fact.
Sancho responds to his master, charging, "I sometimes think that all you tell me of knighthood, kingdoms, empires and island is all windy blather and lies." Yet Quixote diffuses this assertion, saying that all his seeming foolishness is simply the product of enchantments.
Next, the two agree to split up. Sancho will take a letter from Quixote to Dulcinea while the Don will take up penance in the wilderness in the knightly tradition.
Book 1, Part 16: Quixote continues his penance on a mountain peak. Sancho reluctantly returns to the infamous inn, where he speaks to the curate and barber, realizing that he's lost the letter to Dulcinea. He comically tries to rewrite the letter from memory and speaks to them about the island he will be rewarded.
The curate and barber, hearing what Quixote is up to, decide to "free" their friend from his madness by getting him to leave the mountain where he is torturing himself. The curate dresses like a damsel-errant to lure the Don away from the mountain. The barber dresses as her squire. Later, the two switch roles. En route, they meet Cardenio, who details his previously told story.