That evening, Piya goes to the rail and sees flashing lights in the mangroves. She races to knock on Kanai's door and is shocked to see him dressed in a lungi (a sarong-like garment) and vest, looking nothing like himself. Regardless, she invites him to the rail and points to the light show. She says they're glowworms. After a minute, Kanai tells her that he's leaving tomorrow to return to New Delhi. He insists that Fokir didn't maliciously leave him on the island.
Because this light show directly follows Kanai's terrifying experience with the tiger, it drives home the idea that nature is unpredictable: one minute it can be terrifying and in the next, it can be magnificent. Remember that a light show occurred in Nirmal's book by the Christian priest; this foreshadows that some of the other things the priest experienced may come to pass.
Haltingly, Kanai invites Piya to visit him in New Delhi after her survey ends. Piya finds Kanai's tone unsettling; she can't quite reconcile the confident man she met on the train with this one. He admits that he'd like to see her again someplace he's more comfortable. Piya thinks she can't possibly take Kanai's lifestyle in New Delhi seriously, so she says simply that she's not the woman for Kanai.
Though Kanai's tone is never described outright, it's likely that he's simply still unsettled after his run-in with the tiger—again, this shows that being forced to reevaluate how he deals with language has made Kanai far more willing to treat others' languages and modes of communication as worthy of consideration.
Kanai nods and says that he can't put his thoughts into words, just like Moyna can't truly articulate her feelings about Fokir. He explains that Moyna fears that Fokir will leave her for Piya, which annoys Piya. She refuses to answer if she's in love with Fokir and ends the conversation. Looking at the glowworms, she says it was beautiful while it lasted. Kanai says that Nirmal would've called it a tide country mirage.
Piya never defines what "it" is; by leaving this ambiguous, it shows again how spoken language is an often incomplete and unsatisfactory way to describe the world. When Kanai links it then to "tide country mirages," it suggests that this is the work of the natural world and not humans themselves.