Ahab often walks the quarterdeck at night, when only the night-watch sailors are about, since he cannot sleep well in the evenings. The Pequod is drawing toward the Equator and Quito (capital of Ecuador), and the night-air has turned warmer and more pleasant. As Ahab paces the quarterdeck, his ivory leg scrapes against the wood and often wakes the sailors. But when Stubb goes above to tell Ahab, gently, that this is the case, Ahab curses him, calls him a dog, and tells him to “sleep in his grave” below the deck. Stubb takes umbrage at being called a dog, but Ahab again shouts him down, and Stubb retreats to the belowdecks.
One of the under-heralded aspects of the novel is its humor, and in this instance, the reader is reminded that Ahab’s peg-leg would naturally cause the wood to resound below decks as he paces in the night. Stubb appears the best suited, of the three mates, for speaking to Ahab, since Stubb does not feel it necessary to amend his statements in order to please the captain. Yet Stubb is no match for Ahab.
Stubb, talking to himself as he walks back to sleep, says that Ahab is the strangest captain he has ever seen. Stubb also repeats what another sailor has told him: that Ahab’s bunk is often disturbed the morning after he sleeps, indicating that Ahab tosses and turns the whole night long. Stubb wonders what must be wrong with the old man, and vows to find out at some point during the voyage.
Ahab’s inability to sleep soundly will continue throughout the novel, until, by the chase sequence spanning the final three chapters, Ahab is not sleeping at all, but is instead keeping an all-night vigil, in case Moby Dick should reappear at any moment. It is characteristic of Stubb that he is not terrified but more interested or amazed by Ahab's strange behavior.