Forced to migrate in search of food, Korg and his family discover the ocean. Mara's ankle becomes caught under a huge rock while the tide rises around her.
During a drought, a lost girl, Lumi, is befriended by Korg's family. When her father and brother arrive later, they decide to take her back--along with Korg's water.
Bitten by an arachnid, Bok becomes delirious and believes his family are enemies. Korg tries to lure him home where they can care for him until he recovers.
Lacking the skills to hunt and gather food in their new, ocean-side surroundings, the Korg family is watched with amusement and fear by a more local tribe.
Ree discovers a highly-reflective piece of mica. Meanwhile, Korg and Bok make the determination that Korg's youngest son, Tor, is now old enough to join them on the hunts.
A neighboring tribe loses one of their hunters, and Bok wishes to make this man's widow his woman. However, the dead man's brother has a stronger claim to her.
Korg and his family need to cross a wide river or face starvation. After two failed attempts, Mara, afraid, refuses to accompany them on their third attempt.
Wounded by a bear, the near death experience shakes Bok's confidence as a hunter. Bok refuses to hunt again. Without Bok's help the family won't be able to survive, so Korg devises a sneaky plan to help his brother regain his confidence.
Reaching the wide water (the ocean) Korg's family contends with unknown dangers. Her foot is trapped, Mara might soon drown if not freed before high tide. Brute strength fails, but Korg remembers seeing a large stone move once before.
Blinded in a hunting accident, a stranger captures Tor forcing him to be his eyes and lead him back to his own people. Tor tries but can't escape. Soon, Korg and Bok begin to track the missing boy and race to overtake their quarry.
