Chapter 31 of Moby Dick is titled "Queen Mab." It begins with Ishmael discussing the power of dreams and their ability to reveal hidden truths. He reflects on the various beliefs people have held about dreams throughout history and notes that, while they can be confusing and difficult to interpret, they can also be incredibly revealing.

The chapter then shifts to a description of a strange dream that Ishmael has while sleeping in his hammock. In the dream, he encounters a fairy-like creature named Queen Mab, who takes him on a fantastical journey through the world of dreams.

As they travel, Queen Mab shows Ishmael various visions and prophesies, including a vision of Ahab's eventual fate. She also reveals to Ishmael that the true meaning of the white whale goes beyond a mere animal; it is a symbol of the ultimate truth that exists beyond the material world.

The chapter ends with Ishmael awakening from the dream and feeling both exhilarated and deeply unsettled by the experience.

Overall, chapter 31 is a highly symbolic and introspective chapter that explores the power of dreams and their ability to reveal hidden truths about ourselves and the world around us. It also foreshadows the eventual fate of Ahab and deepens the novel's ongoing exploration of the nature of obsession and the search for ultimate truth.