Island of the Blue Dolphins begins with a young girl named Karana who is living on the Island of the Blue Dolphins (fancy name, right?) with her younger brother, Ramo, and sister, Ulape. One day, a group of Russian hunters (Aleutians) land on the island to hunt for otter. This is when the trouble really begins. The people on the island want the hunters to split their booty 50/50. The Aleuts? Not so much, though they agree to the arrangement…for now, anyway.
The relationship between the Aleuts and the island natives grows sour, and soon turns into a full-out argument. In the final argument, Chief Chowig, Karana's father, faces off with Captain Orlov, the leader of the Aleuts. A big fight follows, and 40 native islanders are left dead – including Karana's dad. The nasty hunters take off with their precious otter furs.
On the island, the people – mostly women now – continue to go on with their day-to-day lives. The women take over many of the men's chores, which makes things a bit tense around the village. One of the elders is fed up with the situation and decides to sail to the mainland to find a new, better place to live. He promises to return or to send help.
Sure enough, one day another ship full of white men comes to take everyone away. Hooray? No. More trouble, actually. In the rush to board the ship, Karana's brother, Ramo, gets left behind and the ship starts to leave without him. Ever the protective big sister, Karana jumps off the boat, into the ocean, to stay with Ramo on the island. The two are left all alone on the Island of the Blue Dolphins.
Now, here's where it gets really bad. One morning, Ramo gets up early to go down to the canoes all by himself but, well, he doesn't ever make it to the canoes. A pack of wild dogs attacks and kills Ramo. (We know, right? Terrible.) So now Karana is left all alone on the island – and she vows revenge on the leader of the wild dog pack that killed her little brother.
So this is the beginning of Karana's life all alone on the island. It's almost unbearably lonesome, what with all the memories of the people who used to live there. At first she tries to escape to the mainland using one of the canoes, but her boat is leaky and she has to turn around and return home to the island. (Girl can't catch a break.) Once she reaches the shore, she gives in to living her life on the island – at least until the white men return to rescue her.
Back on shore, there are adventures aplenty. First, Karana confronts the leader of the dog pack, whom she almost kills. But because she's so kindhearted, she nurses the dog back to health and the two become the best of friends. She names him Rontu.
Karana also has an adventure where she attempts to kill a sea elephant for his tusk, which she wants to use as a hunting spear. The sea elephant ends up dying in a fight with another sea elephant, so she does get the tusk. Then she then sets out on a quest to spear a giant devilfish, and does so, but can't drag his body off the shore.
Next, Karana makes some more animal friends. She tames some birds. She becomes friends with an otter named Mon-a-nee. And so forth. It's basically wild kingdom. After Karana becomes friends with the otter, and meets the otter's children, she has a change of heart and decides not to kill any animals anymore. They clearly make for better friends than food.
Eventually, the Aleutian hunters return to the island. Karana hides from them in a cave, but ends up meeting an Aleutian girl (Rontu's former owner, as luck would have it) down by the spring where she gets her water. Though she's worried at first, Karana and the girl – whose name is Tutok – exchange gifts and become friends. The two teach each other words from their native languages and laugh and have a jolly good time together. Once the hunting season is over, though, the Aleuts leave and Karana doesn't even get to say goodbye. After the Aleuts leave, Karana misses Tutok quite a bit and her sister, Ulape, as well.
Things start to go downhill around this time. For starters, Rontu dies. Karana tames another dog, whom she believes to be Rontu's son, but she still misses Tutok and Ulape more and more each day. Next up, an earthquake strikes the island, followed by a series of huge tidal waves (we would probably call this a tsunami today). Karana manages to survive all of this. And then? A group of white men return to the island, but Karana can't catch them in time before they hop on their boat. Bah!
Fortunately, the men return to the island a few years later and rescue Karana and her dog – at last. Before the men let her on the boat, though, they measure her for a new dress – one that covers her from head to toe. Karana boards the boat with her dog, all dolled up in her new dresses, and watches the island as the ship pulls away. She thinks of the happy times she had there. The book ends, and we're left wondering what will happen to Karana when she reaches the mainland.