Two days later, Don Quixote and Sancho reach the clear river Ebro. Don Quixote ponders what he had seen in the Cave of Montesinos. He believes his vision was true, whereas Sancho believes it all to be lies.
They find a boat tied up. Don Quixote orders Sancho to secure their steeds. He believes the boat was placed there by enchanters to transport him to a place where he is needed. Sancho says he'll obey, but he reckons the boat belongs to a fisherman. He is uneasy about leaving their steeds behind.
Rocinante tries to escape, and Dapple starts braying. Sancho starts weeping, and Don Quixote calls him a coward. Sancho gets in, but they don't make much progress with the gentle current.
Soon though, Don Quixote sees what he believes to be a castle. Sancho says they are mills. The millers rescue them from being mauled by the river wheels. Don Quixote begins to fight them, seeing them as villains. The millers knock them into the water, then rescue them. The boat is damaged, and the millers demand that Quixote pay them for damages. He promises to pay them as soon as they deliver their captive.
Don Quixote decides the mission is hopeless when people are enchanted into believing there is no castle but a mill. He apologizes to the captives. Obviously this is meant for another knight.
Sancho pays the millers for the lost boat, lamenting the expense of it. The millers and fishermen become convince they are madmen and leave.