The men administer doses of the remedy every three hours, and over the course of the next day, Harbert shows visible signs of improvement. Harbert is almost completely healed by the end of January, and the men plan an expedition for mid-February to rid the island of the pirates once and for all.

The day of their departure arrives, and the whole company leaves—including Top and Joop—leaving Granite House unoccupied. Passing through the jungle, they discover traces of their prey, even finding a campsite, but they do not discover the pirates on their trek all the way to the western shore of the island.

They decide to head to Mount Franklin, determining that it would be the likeliest place for the pirates to set up a more permanent camp. Along the way, Gideon and Pencroff take a short detour to see if the sheepfold has been reoccupied. Arriving at the gate, they discover it locked and the house barricaded. Returning to the other men, they bring the whole company back to launch an assault on what they presume to be the last of the pirates. When they return to the sheepfold, however, they find one of the doors has been opened, and when they carefully approach the building, they discover their long-lost companion, Ayrton, inside.