The Maelstrodomus sails north from the Southern Eye toward the vortex at Galdemol while strands of the broken Ithelion fall around the ship and restore the Harbingers' light and darkness boons. Below deck, Torrin brings his warhammer to Ilk, who explains that its story remains unwritten and describes the Black Worm as an eater of dreams that can return lost memories at great risk. Torrin declines another vision for now. Bjorn tells the others that Mathias wants Normandy to pass through the Dio Ostium and has offered limitless prosperity for Bjorn's people in exchange. Later, Mathias and the Queen of Dusk draw Vyr into a private vision, warn that her growing hunger could turn her against the others, and urge her to take her power seriously. By morning, a fogbound island has appeared to the northeast. Sailors identify it as the lost Isle of Ilf and beg the party not to approach, but the Harbingers choose to investigate.

An Ilferan shaman meets the landing party and uses the sea to reveal a clam containing a black pearl. Ilferan warriors lead the Harbingers through the jungle to a village built around a cavern, where a chieftain and another shaman prepare a ritual beside a deep pool and four green obelisks. The islanders thank the visitors for choosing a sacrifice, summon a creature called the Dredged, and use the obelisks to siphon darkness from Bjorn into the pearl. The Harbingers fight the warriors and shaman while destroying the obelisks. When the final obelisk falls, Bjorn is freed, but the chieftain throws the pearl into the water. A smooth, gray, web-handed creature rises from the depths and drains the chieftain, splitting his soul as the remaining islanders pray to the Tangled One. Normandy retrieves the pearl with Mage Hand. When the creature attempts to drain him, an unseen voice repels it and says, "Not yet, Angie."

A violent storm overtakes the village as barnacles spread, butchered sea life begins moving again, and a song calls the Harbingers back toward the cavern. They flee through the jungle while the young shaman from the beach tackles Helena and demands to be taken with them. The Harbingers bring her aboard their dinghy and row toward the Maelstrodomus as shadows pour from the cavern and the Dredged pursues them through the water. Proximity to Helena's refilled vial allows the others to cast light upon seaweed, oars, and the boat itself. Their illuminated vessel clears the reef that stops the creature, and the crew hauls the party and their frightened Ilferan passenger safely aboard. Bjorn's stolen darkness remains sealed within the black pearl in Normandy's possession.