March 1865. In the United States, during the Civil War, five daredevils-northerners flee a balloon from the southerners of Richmond. A terrible storm throws four of them onto the shore of an uninhabited island in the Southern Hemisphere. The fifth man and his dog are hiding in the sea off the coast. This fifth - a certain Cyres Smith, a talented engineer and scientist, the soul and leader of a group of travelers - unwittingly keeps his companions in tension for several days, who can not find anywhere either him or the dog Top devoted to him. The former slave suffers most of all, and now the loyal servant of Smith is the Negro Nab. In the balloon were also a war journalist and Smith's friend, Gideon Spilet, a very energetic and decisive man with a seething mind; sailor Pencrof, a good-natured and adventurous daredevil; Fifteen-year-old Harbert Brown, the son of the captain of the ship on which Pencrof sailed, remained an orphan, and to whom the sailor treats as his own son. After a tiring search, Nab finally finds his inexplicably saved host, a mile from the coast. Each of the new settlers of the island has irreplaceable talents, and under the leadership of Cyres and Spilet, these brave people rally and become a united team. First, with the help of simplest means at hand, then producing in their own small factories more and more complex objects of labor and household goods, settlers equip their lives. They hunt, collect edible plants, oysters, and then even breed domestic animals and engage in farming. They arrange housing for themselves high in the rock, in a cave freed from water. Soon, thanks to their hard work and intelligence, the colonists no longer know the need for food, clothes, warmth and comfort. They have everything except news of their homeland, the fate of which they are very worried about.

Once, returning to their dwelling, called by them the Granite Palace, they see that monkeys are bossing inside. After a while, as if under the influence of insane fear, the monkeys begin to jump out of the windows, and someone’s hand throws the rope ladder that the monkeys raised into the house. Inside, people find another monkey - an orangutan, which they keep and call Uncle Jupe. In the future, Jupe becomes a friend, servant and indispensable helper to people.

On another day, settlers find in the sand a box with tools, firearms, various appliances, clothes, kitchen utensils and books in English. Settlers wonder where this box could come from. From the map, which also appeared in the box, they find that next to their island, on the map not marked, is the island of Tabor. The sailor Pencrof is eager to go to him. With the help of his friends, he builds a bot. When the bot is ready, all together they go on it for a test voyage around the island. During it, they find a bottle with a note saying that the shipwrecked man is waiting for salvation on the island of Tabor. This event strengthens Pencroff’s confidence in visiting a neighboring island. Pencrof, journalist Gideon Spilet and Harbert set sail. Arriving at Tabor, they discover a small shack where, by all indications, no one has been living for a long time. They scatter around the island, not hoping to see a living person, and try to find at least his remains. Suddenly they hear Harbert scream and rush to his aid. They see Harbert struggling with some kind of monkey-grown creature. However, the monkey turns out to be a feral man. Travelers bind him and transport him to their island. They give him a separate room in the Granite Palace. Thanks to their attention and concerns, the savage soon turns back into a civilized man and tells them his story. It turns out that his name is Ayrton, he is a former criminal, he wanted to take possession of the Duncan sailing ship and with the help of the same dregs of society he turned into a pirate ship. However, his plans were not destined to come true, and as a punishment twelve years ago he was left on the uninhabited island of Tabor, so that he would realize his deed and atone for his sin. However, the owner of the "Duncan" Eduard Glenarvan said that someday he would return for Ayrton. The settlers see that Ayrton sincerely repents of his past sins, and he tries to be useful to them in every way. Therefore, they are not inclined to judge him for past misconduct and willingly accept him in their society. However, Ayrton needs time, and therefore he asks for an opportunity to live in the coral that the settlers built for their domesticated animals at some distance from the Granite Palace.

When the bot returned to the storm from Tabor Island at night, it was saved by a bonfire, which, as they thought, floating on it, was kindled by their friends. However, it turns out that they were not involved in this. It also turns out that Ayrton did not throw a bottle of note into the sea. Settlers cannot explain these mysterious events. They are increasingly inclined to the idea that, besides them, on the island of Lincoln, as they christened him, there is someone else, their mysterious benefactor, who often comes to their aid in the most difficult situations. They even embark on a search expedition in the hope of locating his place of residence. However, the search ends to no avail.

The next summer (for since the time that Ayrton appeared on their island, and before he told them his story, five months have already passed and the summer is over, and it’s dangerous to sail in the cold season), they decide to get back to Tabor Islands to leave a note in the hut. In the note, they intend to warn Captain Glenarvan if he returns that Ayrton and five other wrecked victims are waiting for help on a neighboring island.

Settlers have been living on their island for three years. Their life, their economy reached prosperity. They are already harvesting rich crops of wheat grown from a single grain, which was found in Harbert’s pocket three years ago, built a mill, raised poultry, completely equipped their dwelling, made new warm clothes and blankets for themselves from mouflon wool. However, their peaceful life is overshadowed by one incident that threatens them with death. Once, looking at the sea, they see a well-equipped ship in the distance, but a black flag flies above the ship. The ship anchors off the coast. It shows beautiful long-range guns. Ayrton sneaks into the ship under cover of night to carry out reconnaissance. It turns out that there are fifty pirates on the ship. Miraculously slipping away from them, Ayrton returns to the shore and tells his friends that they need to prepare for the battle. The next morning two boats descend from the ship. On the first, the settlers shoot three, and she returns, the second lands on the beach, and the six remaining pirates on her hide in the forest. The cannons are scorched from the ship, and it comes even closer to the shore. It seems that nothing has the power to save a handful of settlers. Suddenly a huge wave surges under the ship, and it sinks. All pirates on it die. As it turns out later, the ship was blown up by a mine, and this event finally convinces the inhabitants of the island that they are not alone here.

At first, they are not going to exterminate the pirates, wanting to give them the opportunity to lead a peaceful life. But it turns out that the robbers are not capable of this. They begin to rob and burn the settlers' households. Ayrton goes to the coral to visit the animals. Pirates grab him and take him to a cave, where they want to torture him to agree to go to their side with torture. Ayrton doesn't give up. His friends go to his aid, but are seriously injured in Harbert’s coral, and his friends remain in him, unable to go back with the young man who was dying. After a few days, they still leave for the Granite Palace. As a result of the transition, Harbert begins a malignant fever, he is at death. Once again, providence intervenes in their lives and the hand of their good mysterious friend throws them the necessary medicine. Harbert is fully recovering. The settlers intend to deliver the final blow to the pirates. They go to the coral, where they intend to find them, but find Ayrton, who is exhausted and barely alive, and nearby, the corpses of robbers. Ayrton reports that he does not know how he ended up in the coral, who brought him from the cave and killed the pirates. However, he reports one sad news. A week ago, the bandits went to sea, but, not knowing how to control the bot, broke it on the coastal reefs. The trip to Tabor has to be postponed until the construction of a new vehicle. Over the next seven months, the mysterious stranger does not make itself felt. Meanwhile, a volcano wakes up on the island, which the colonists thought was already dead. They are building a new large ship, which, if necessary, could deliver them to inhabited land.

One evening, already getting ready to go to bed, the inhabitants of the Granite Palace hear a bell. The telegraph that they spent from the coral to their home is working. They are urgently called into the coral. There they find a note asking them to go along the extra wire. The cable leads them to a huge grotto where, to their amazement, they see a submarine. In it, they meet with their master and their patron, captain Nemo, the Indian prince Dakkar, who has been fighting for the independence of his homeland all his life. He, already a sixty year old man who buried all his associates, is near death. Nemo gives new friends a casket with jewels and warns that when the volcano erupts, the island (such is its structure) will explode. He dies, the settlers turn up the hatches of the boat and lower it under the water, and they build the new ship tirelessly all day long. However, they do not have time to finish it. All life perishes during the explosion of the island, from which only a small reef in the ocean remains. Settlers, who spent the night in a tent on the shore, are cast into the sea by an air wave. All of them, with the exception of Jupe, remain alive. For more than ten days they have been sitting on the reef, almost dying of hunger and no longer hoping for anything. Suddenly they see a ship. This is Duncan. He saves everyone. As it later turns out, Captain Nemo, while the bot was still intact, floated on it to Tabor and left a note to the rescuers.

Returning to America for jewelry donated by Captain Nemo, friends buy a large piece of land and live on it the same way they lived on Lincoln Island.