Nirmal resumes his account in the notebook. At Kumirmari, he first hears about Morichjhãpi. People suggest that things won't end well, and Nirmal puts it out of his mind. He and Horen begin their journey back to Lusibari, but are held up when a storm suddenly picks up. Horen steers them to the nearest island—Morichjhãpi—and they approach the nearest dwelling and ask for shelter. A young woman opens the door and recognizes Nirmal, though she has to explain that she's Kusum before he recognizes her. Nirmal calls Horen inside and they make small talk about her son, Fokir, and about Horen's children. Finally, Nirmal asks Kusum to tell him her story.
It becomes clear very soon that being washed up on Morichjhãpi is a major defining moment for both Nirmal and Horen. It's notable, then, that what brings them to the island in the first place is a storm—something that reinforces the power of the natural world. However, given the way that the novel suggests that nature will always triumph over humans, it foreshadows that the human events that take place on Morichjhãpi are very much out of anyone's control.
Kusum's mother was in a town called Dhanbad, so Kusum boarded a train and went there. Fortunately, she met a man at the station from tide country named Rajen. He'd been disabled after being hit by a bus, and he invited her to stay in his shack. He proved himself good and kind, and helped Kusum find her mother. When Kusum and her mother finally met, her mother was thin and drawn. She told Kusum to come see her once more, but then to go home.
The fate of Kusum's mother reinforces that women in this society are at the mercy of both the natural world and the predatory men around them. It's luck, then, that Kusum meets someone as good and kind as Rajen, as the power of the natural world would otherwise suggest that things are out of Kusum's control.
When Kusum and Rajen went back, Rajen suggested that he and Kusum marry so that they could care for Kusum's mother. Both Kusum and her mother were thrilled, though Kusum's mother died months later. They had Fokir, but three years later, Rajen fell from a train and died. Kusum felt that Bon Bibi was with her when she heard not long after of a "great march to the east." The march came through Dhanbad, and Kusum took a few marching women into her house to care for them. The women told Kusum of being moved to a horrific settlement and spending years longing for the tide country mud that runs through their veins. Now, they're on their way to an island called Morichjhãpi. Kusum decided to go with them.
When the marching women state that the tide country mud runs through their veins, it shows that locals of the Sundarbans view themselves as intrinsically part of nature, even as they do their best to keep themselves safe from nature's violent outbursts. This suggests that seeing themselves as part of the natural world is one way to deal with the intense anxiety they surely experience living in such a dangerous environment, and that belief makes living there seem more palatable.