By sunset, Piya checks her GPS and sees they're about seven miles from Garjontola. She figures that Horen won't be worried, and she and Fokir find a spot to stop for the night. The moon rises not long after, and Fokir points out a faint halo of colored light around the moon. He gestures that it was a moon rainbow. Piya studies the water and wonders if Fokir understands how inspiring and constant he is, and she wonders if she'd ever be able to offer him anything close to what he has with Moyna.
Because the reader is well aware that there's a cyclone coming and Piya and Fokir don't know this, the next chapter works to build anxiety and tension given that it's clear that Piya will be surprised by what's to come. It is strange, however, that Fokir apparently has no sense of what's to come, given his intimate connection to nature. This suggests that there may be more to this than Fokir simply not knowing what’s to come.
Piya and Fokir sit unmoving for a while. Finally, he takes her hand for a moment and then goes to prepare dinner. Piya accepts the food and feels as though the rainbow brought something in their relationship to an end. After dinner, she pulls out Kanai's letter and begins to read. He begins with a question of what it means for a man to give a woman something that only she will ever value, and says he's currently struggling with the question. He writes that he learned at Garjontola what it means to want to give someone else happiness at the cost of his own, and admits he lied when he said he couldn't translate Fokir's chanting. It was part of The Glory of Bon Bibi, which Fokir has had memorized since he was a child. Kanai explains that this story is the one that brought the Sundarbans to life long ago.
With Fokir's touch, Piya and Fokir are able to acknowledge the fact that they do indeed have feelings for each other. Notably, this single touch says more than Fokir and Piya would've been able to verbally discuss. When Kanai suggests that translating The Glory of Bon Bibi for Piya is a selfless act, it suggests that Fokir's trick with the tiger had a profound effect on Kanai: now, Kanai truly sees Piya as a person, not just a conquest.
Kanai begins the story at the part where Dhona sacrifices Dukhey to Dokkhin Rai. Dokkhin Rai comes to Dhona in a dream and instructs Dhona to return to the island, say his name, and not touch the beehives in the jungle. The next day, Dhona leaves Dukhey and takes his men to the forest. When Dhona does as he's told, the bees swarm and demons load Dhona's boats with honey. Then, Dokkhin Rai unloads the honey and instead, loads the boats with valuable wax. With this, the demon disappears.
Dokkhin Rai is a tiger demon, making him a stand-in for the dangerous nature of the natural world as a whole. This whole tale then becomes a cautionary story to not trust the apparent generosity of the natural world, as it will inevitably come at a price—often, a human price.
Dukhey, meanwhile, struggles to cook a meal and asks Bon Bibi for help. She arrives, and with a pass of her hand, creates a sizzling feast. When Dhona and the crew arrive, Dhona begins to wonder if Bon Bibi had a hand in the meal, but ultimately thinks little of it. In the morning, Dhona sends Dukhey to gather firewood on the shore. Dukhey tries to refuse, but finally complies. Dokkhin Rai assumes his tiger form and stalks the boy. As the demon pounces, Dukhey calls on Bon Bibi. She arrives with Shah Jongoli, who hits the tiger and sends it racing away into the forest.
The legend of Bon Bibi helps the residents of the Sundarbans feels slightly more at home in a world that, to an outsider, seems as though it's out to get them at every turn. With this, the novel shows how stories have the power to make people feel more comfortable with themselves and their homes by giving them the tools to communicate with the natural world.
When Piya finishes reading, Fokir joins her in the middle of the boat. She touches him and asks him to sing for her. He does, and Piya feels as though she's surrounded by Fokir's voice and the meaning that Kanai gave it. She turns over the final page, where Kanai left a Rilke quote about love being rooted in the past and in the natural world.
The emotions that Piya feels here are the product of being able to rely on a number of different languages and forms of communication to understand the world around her. With this, the novel shows that the more modes someone has to communicate and understand, the better and richer life can be.