Jim Hawkins is a young boy who lives at his parents’ inn, the Admiral Benbow, near Bristol, England, in the eighteenth century. An old sea captain named Billy Bones dies in the inn after being presented with a black spot, or official pirate verdict of guilt or judgment. Jim is stirred to action by the spot and its mysterious, accurate portent of Billy’s death. Hastily, Jim and his mother unlock Billy’s sea chest, finding a logbook and map inside. Hearing steps outside, they leave with the documents before Billy’s pursuers ransack the inn.
Jim realizes that the contents he has snatched from the sea chest must be valuable, so he takes one of the documents he has found to some local acquaintances, Dr. Livesey and Squire Trelawney. Excited, they recognize it as a map for a huge treasure that the infamous pirate Captain Flint has buried on a distant island. Trelawney immediately starts planning an expedition. Naïve in his negotiations to outfit his ship, the Hispaniola, Trelawney is tricked into hiring one of Flint’s former mates, Long John Silver, and many of Flint’s crew. Only the captain, Smollett, is trustworthy. The ship sets sail for Treasure Island with nothing amiss, until Jim overhears Silver’s plans for mutiny. Jim tells the captain about Silver and the rest of the rebellious crew.
Landing at the island, Captain Smollett devises a plan to get most of the mutineers off the ship, allowing them leisure time on shore. On a whim, Jim sneaks into the pirates’ boat and goes ashore with them. Frightened of the pirates, Jim runs off alone. From a hiding place, he witnesses Silver’s murder of a sailor who refuses to join the mutiny. Jim flees deeper into the heart of the island, where he encounters a half-crazed man named Ben Gunn. Ben had once served in Flint’s crew but was marooned on the island years earlier.
Meanwhile, Smollett and his men have gone ashore and taken shelter in a stockade the pirates have built. Jim returns to the stockade, bringing Ben with him. Silver visits and attempts a negotiation with the captain, but the captain is wary and refuses to speak to him. The pirates attack the stockade the next day, and the captain is wounded. Eager to take action, Jim follows another whim and deserts his mates, sneaking off to hunt for Ben’s handmade boat hidden in the woods.
After finding Ben’s boat, Jim sails out to the anchored ship with the intention of cutting it adrift, thereby depriving the pirates of a means of escape. He cuts the rope, but he realizes his small boat has drifted near the pirates’ camp and fears he will be discovered. By chance, the pirates do not spot Jim, and he floats around the island until he catches sight of the ship drifting wildly. Struggling aboard, he discovers that one of the watchmen, Israel Hands, has killed the other watchman in a drunken fit. Jim takes control of the ship, but Israel turns against him. Jim is wounded but kills Israel.
Jim returns to the stockade but finds it occupied by the pirates. Silver takes Jim hostage, telling the boy that the captain has given the pirates the treasure map, provisions, and the use of the stockade in exchange for their lives. Jim realizes, however, that Silver is having trouble managing his men, who accuse him of treachery. Silver proposes to Jim that they help each other survive by pretending Jim is a hostage. However, the men present Silver with a black spot and inform him that he has been deposed as their commander.
In a desperate attempt to gain control of his crew, Silver shows them the treasure map to appease them. Silver leads Jim and the men to the treasure site, but they are shocked to find it already excavated and the treasure removed. The men are angered and near mutiny again. At that moment Dr. Livesey, Ben Gunn, and the others fire on the pirate band, which scatters throughout the island. Jim and Silver flee, and are guided by the others to Ben’s cave, where Ben has hidden the treasure, which he had discovered months before.
After spending three days carrying the loot to the ship, the men prepare to set sail for home. There is a debate about the fate of the remaining mutineers. Despite the pirates’ submissive pleas, they are left marooned on the island. Silver is allowed to join the voyage, but he sneaks off the ship one night with a portion of the treasure and is never heard from again. The voyage home comes to a close. Eventually, Captain Smollet retires from the sea, and Ben becomes a lodge-keeper. Jim swears off treasure-hunting forever and suffers from nightmares about the sea and gold coins.