Twelve-year-old Karana is gathering roots with her six-year-old brother, Ramo, when they catch sight of a red ship in the distance. Karana, Ramo, and their older sister Ulape are part of a tribe that lives on the Island of the Blue Dolphins, a small, dolphin-shaped island surrounded by kelp beds. When the ship drops anchor and the men come to shore, the Russian Captain Orlov and his Aleut otter hunters negotiate with Karana’s father, Chief Chowig. Chief Chowig remembers a Russian otter hunting expedition years ago that didn’t end well, so he’s unwilling to let Captain Orlov hunt without compensating the tribe. Captain Orlov eventually agrees to share 50% of the profit from the pelts with the tribe, in the form of jewelry and weapons.
Over the next few months, Karana’s tribe keeps close watch on the Aleuts. Finally, the tribe notices the Aleuts packing up. Chief Chowig confronts Captain Orlov, since Orlov hasn’t paid up yet. The men argue, and a battle breaks out on the beach. Karana’s father dies in the battle, along with two-thirds of the tribe’s men. Captain Orlov leaves, giving the tribe only a single chest of beads.
The next few months are difficult. The new chief, Kimki, allows women to hunt and fish since there aren’t enough men to complete the tasks, but the remaining men in the tribe resent the women’s success. In the spring, Kimki takes a canoe east, promising to return for the rest of the tribe. As summer approaches, Kimki’s successor, Matasaip, urges the tribe to prepare to flee in case the Aleuts return. But when a ship arrives, it’s not the Aleuts—it’s white men that Kimki sent, come to take the tribe across the sea. When Karana gets on the ship, she realizes that Ramo is still on the island. She leaps into the sea and swims to shore, figuring the ship will return for them soon.
Ramo immediately crowns himself the new chief, but a day after he and Karana are left on the island, he goes out by himself and a roaming pack of wild dogs kills him. Karana vows to kill the wild dogs, once she has a place to live and weapons to protect herself. She burns the huts in the village and takes up residence on the headland, sleeping on a tall rock where the dogs can’t reach her.
Karana’s lack of weapons poses a problem: women in her tribe aren’t allowed to make them. Karana searches her neighbors’ huts for weapons that were left behind and even digs through the chest that Captain Orlov left in case she finds the spearheads he’d promised. She doesn’t; the chest contains only jewelry. Finally, Karana decides she must make weapons herself, even if doing so might invite earthquakes, floods, or high winds. She makes a bow and arrows and a spear, which makes her feel safe.
When summer rolls around, Karana waits for the ship to return for her. When it doesn’t, she decides to take a canoe and head east herself. The canoe starts to leak overnight and finally, Karana decides to turn back—it’s too dangerous to continue. When she returns to the island, she decides that this is her home. She’ll be here until the white men return.
Karana decides to make her home on the headland. She makes a fence of whale ribs, a house, and cooking utensils. By spring, she’s ready to kill the wild dogs. This means she must make a better spear, which requires acquiring a sea elephant tooth for the point. Her trip to the sea elephants ends badly—she doesn’t kill one and ends up tripping and hurting her leg. She spends six days recovering in a cave near the spring so she has access to water; when she’s better, she turns the cave into a second home where she can live when she’s ill. When she returns to the sea elephants’ beach, she discovers a dead sea elephant bull’s carcass and takes his teeth.
More than anything, Karana wants to kill the pack’s leader. This dog came with the Aleuts, and he’s bigger than the wild dogs that have always lived on the island. Karana manages to shoot the dog in the chest and then track him for several days. But just as Karana prepares to kill the dog, she finds she can’t. She carries him home, tends to his wounds, and discovers that she likes having another creature around. She names him Rontu.
In case the Aleuts return, Karana needs a canoe. She refurbishes an old canoe so it’s small enough to handle. Once it’s finished, she and Rontu spend their days exploring the island and its sea caves. Karana finds a cave under the headland that’s perfect for storing her canoe, and there, she also sees a giant devilfish (octopus). She decides to spend the winter making the special spear that will allow her to kill it, as devilfish are a delicacy.
The spring is a happy time for Karana and Rontu. Rontu engages in a final fight with the dog pack and doesn’t leave Karana’s side again, and Karana tames two brightly colored songbirds, Tainor and Lurai. Karana collects abalone for the winter and, one day, she spots the devilfish on the reef. She spears it, but in the ensuing battle with the massive creature, both she and Rontu sustain injuries. Though Karana manages to kill the devilfish, she doesn’t have the strength or will to take it home—and she never tries to kill a devilfish again.
Later in the summer, Karana discovers Black Cave—a cave where some of her ancestors’ remains rest—and visits Tall Rock, where she kills 10 cormorants. She’s going to make a skirt with their skins and feathers. On the way home from Tall Rock, Karana spots the Aleut ship. She packs her things, makes her house look abandoned, and holes up in the cave near the spring with Rontu. Karana spends most days in the cave, sewing her cormorant skirt by the light of burning fish. She stays hidden because the Aleuts have a girl with them, and Karana is afraid the girl will find her. But one day, near the end of summer, Karana is working on her skirt outside when the girl appears at the top of the ravine. Karana doesn’t trust the girl, who introduces herself as Tutok. But that night, Karana finds a necklace of beautiful beads left outside her cave. Over the next few days, Karana and Tutok become friends. They laugh together and exchange words in each other’s languages. Tutok doesn’t return one day, and Karana knows the Aleuts left. Though she’s glad to have the island to herself again, she misses Tutok and feels lonely.
The Aleuts left a lot of otter wounded; Karana kills most to put them out of their misery. But she finds one that’s not injured too badly and puts him in a tidepool so he can heal. Karana and Rontu catch fish for the otter, and she names him Mon-a-nee— “little boy with large eyes.” The weather is too bad to fish for a few days, and when Karana returns to the tidepool, Mon-a-nee is gone. Karana feels increasingly lonely.
In the spring, Karana tames several more birds and throws herself into gathering abalones—she wants to be prepared early if the Aleuts return. During one trip to gather abalones, Mon-a-nee shows himself to Karana. He finds her again several months later and shows her his two babies. Karana realizes that Mon-a-nee is female and renames her Won-a-nee. After this summer, Karana stops killing animals, even those she doesn’t like. All animals, she realizes, could become her friends, and they make the world a happier place.
Years pass. The otter leave the Island of the Blue Dolphins every summer in anticipation of the Aleuts’ returning, but one summer, they stay—all the otter who remember the Aleuts must be dead. Karana stops keeping track of the months she’s been on the island. Late in the summer, Rontu dies, and Karana buries him on the headland with his favorite stick. In the spring, she manages to capture another dog whom she believes is Rontu’s son. She names him Rontu-Aru, which means “son of Rontu,” and it’s sometimes hard to remember that he isn’t Rontu. Karana thinks often of Ulape and Tutok and hears their voices in the wind.
In the spring, the weather suddenly becomes hot and oppressive. Since Rontu-Aru doesn’t like the heat, Karana leaves him at home while she goes to the sandspit to repair her canoe. While she’s on the beach, Karana hears a rumble—and sees a huge wave coming toward the island. Karana holds onto the cliffs as two waves hit the island, and then she runs home in the morning. That evening, earthquakes begin to shake the island, but fortunately they don’t cause too much damage.
The tidal wave destroyed Karana’s canoe, so she sets to work making a new one. It takes her most of the spring to do this. As she’s on the beach, preparing to finish the canoe, she spots a ship she’s never seen before. It’s not the Aleuts, but Karana doesn’t know if it’s the men sent by her tribe. Figuring the men on this ship are looking for her, Karana dresses in her cormorant skirt, packs her things, and heads for the beach—but a storm is rolling in, and the men have already left the island.
Two years later, the ship returns. Karana again dresses in her fine clothes, packs her things, and waits for the three men to find her. The men speak the oddest-sounding language Karana has ever heard, but she’s happy to hear another voice. One man makes her a scratchy blue dress, which Karana wears even though she doesn’t like it. When the men ask where they can find otter to hunt, Karana pretends not to understand (the otter are hiding at Tall Rock). Nine days later, the ship sails with Karana aboard. Karana thinks of her happy days on the island as she sits with Rontu-Aru, watching the Island of the Blue Dolphins disappear in the distance.
