After months apart, Roz and Brightbill reunite in the Nest. Roz builds a fire, and Brightbill tells Roz the story of his winter migration with the flock.

Brightbill explains that the flock first flew over the ocean, rested on small islands, and reached the mainland. Early snow caught the geese off guard, making food and water hard to find and weakening the flock. Old Widefoot dies in the first storm, but Longneck keeps the geese moving by reminding them that geese keep going.

Lost and desperate, the flock finds a farm with a greenhouse tended by a robot that looks like Roz. Brightbill slips inside, discovers warmth and food, and meets an old cat named Snooks, who helps the flock hide there. Brightbill also explores a barn filled with caged animals and working robots, learning more about the human world.

The refuge ends when an angry human discovers the geese in the greenhouse. Longneck tries to defend the flock, but the human fires a rifle that shoots a bright beam and kills him. Brightbill opens the greenhouse door, and the terrified flock escapes into the cold.

With Longneck dead, the flock chooses Brightbill as its new leader. Unsure but determined, Brightbill repeats Longneck’s words and leads the flock south. Along the coast and through a city, the geese see many humans, robots, ships, and buildings; a pigeon named Graybeak guides them and shows Brightbill a factory where robots like Roz are being built.

After leaving the city, the flock finally reaches the warm wintering grounds, where they meet other geese and learn that many flocks suffered losses from the strange winter weather. In spring, Brightbill leads the flock north by the usual route, avoids humans and robots, and returns to the island, the pond, and Roz.