An old sailor, calling himself "the captain" but really called Billy Bones, comes to lodge at the Admiral Benbow Inn on the English coast during the mid 1700s, paying the innkeeper's son, Jim Hawkins, a few pennies to keep a lookout for "seafaring men." One of these shows up, frightening Billy (who drinks far too much rum) into a stroke, and Billy tells Jim that his former shipmates covet the contents of his sea chest. After a visit from another man, Billy has another stroke and dies; Jim and his mother (his father has died only a few days before) unlock the sea chest, finding some money, a journal, and a map. The local physician, Dr. Livesey, deduces that the map is of an island where the pirate Flint buried a vast treasure. The district squire, Trelawney, proposes buying a ship and going after the treasure, taking Livesey as ship's doctor and Jim as cabin boy.
Several weeks later, Trelawney sends for Jim and Livesey and introduces them to Long John Silver, a Bristol tavern-keeper whom he has hired as ship's cook. They also meet Captain Smollett, who tells them that he does not like the crew or the voyage, which it seems everyone in Bristol knows is a search for treasure. After taking a few precautions, however, they set sail for the distant island. During the voyage the first mate, a drunkard, disappears overboard. And just before the island is sighted, Jim overhears Silver talking with two other crewmen and realizes that he and most of the others are pirates and have planned a mutiny. Jim tells the captain, Trelawney, and Livesey, and they calculate that they will be seven to nineteen against the mutineers and must pretend not to suspect anything until the treasure is found, when they can surprise their adversaries.