With bad weather setting in, the family takes up residence at Tenthurst for the next few months. The winds have been causing huge ocean swells, and the skies are almost always gray with thick clouds.

Because of the low light, the cave house they have built feels oppressive. To remedy this, the father and Jack rig a new light. They find a bamboo pole that will reach from the floor to the ceiling. Then after securing it, Jack climbs to the top of the pole and hangs a large oil lamp that they had rescued from the ship. The artificial light fills the cave, making the room feel more comfortable.

Since the weather is not conducive to outdoor activities, the family spends their time arranging the interior rooms of the cave. Ernest and Franz set up a library, sorting and then placing the family's collection of books on shelves their father has made. Elizabeth and Franz set up the kitchen, while the father and Fritz organize a workshop. During this time, the family also opens for the first time the boxes and chests that had been salvaged from the ship. The atmosphere created by the uncovering of new treasures makes everyone's spirits rise. In the chests they find mirrors, chairs, writing tables, and even a music box. With these new treasures, the cave house quickly becomes very festive.

Finally the storms cease, and the family wanders outdoors. Fritz, being one of the more curious members of the family, walks over to Flamingo Marsh, where he notices what looks like a boat turned upside down on the beach. When he draws nearer, he is surprised to find that what he thought was a boat turns out to be a beached whale.

When the other boys and the father approach, they are amazed at the size of the whale. The boys wonder what they can do with it, not thinking that it could be eaten. Their father tells them that to make the best use of the whale, they will process the blubber to use as fuel for their lanterns.

As they work at collecting the blubber, the family constantly remarks on the size of the whale. The father estimates that it is at least sixty-five feet long; its wide jaw alone is at least sixteen feet long, and the whale must have weighed 50,000 pounds. As they continue their work, the father educates his sons about the physiology of the whale. He tells them that the whale is not a fish, as they had supposed. The boys are also curious about how small the whale's throat is, especially in comparison to its wide mouth. Their father explains how the whale exists by diving through the water with its mouth open, engulfing masses of small sea creatures, such as shrimp.

Before leaving the whale carcass for the scavenger birds to feast on, the father cuts through the whale to its intestines. He thinks the intestines might serve as a perfect container for all the whale oil they are about to process. This job is very bloody, and the father and the boys are glad to get back to their house so that they can bathe.