Jim Hawkins joins Squire Trelawney and Doctor Livesey in the coastal town of Bristol to prepare for their treasure hunt.
Because this novel has a lot of plot, the set-up requires a fair amount of time. And by "a fair amount of time," we mean about nine chapters. First Jim has to encounter Billy Bones, take the treasure map over Billy's dead body, and pass it along to Doctor Livesey and Squire Trelawney. Then the novel has to get Jim Hawkins in the same city as Doctor Livesey and Squire Trelawney – and his future frenemy, Long John Silver – to prepare for their voyage to Treasure Island. At this initial stage, Jim is completely taken in by Long John Silver's style and appearance of kindliness.
Captain Smollett warns Squire Trelawney that something is wrong with the crew.
Before the Hispaniola leaves Bristol Harbor, Captain Smollett tells Squire Trelawney that something fishy is going on. The captain is an experienced man, and he can see that the crew Squire Trelawney has hired (with Long John Silver's help) is undisciplined and spoiled. Of course, Squire Trelawney doesn't listen to him (and Jim also thinks Captain Smollett is worrying over nothing), but we readers start to suspect that there is something wrong on board the Hispaniola.
Jim overhears Long John Silver explaining his evil plan to Dick Johnson and Israel Hands.
Up until Chapter 11, we've gotten hints and signs that something piratical is happening on board the Hispaniola: in addition to Captain Smollett's stated suspicions, we also know that Squire Trelawney has blabbed their plans all over town, against Doctor Livesey's express advice. And they are following a dead pirate's map, so that right there is risky. But the plot really starts to thicken when Jim happens to fall asleep in an apple barrel on deck. There he wakes up to overhear Long John Silver's recruitment speech to Dick Johnson. Long John Silver also explains his long-term plan to wait until they reach Treasure Island, murder all the non-pirates, then take the gold for themselves. So now we know that Long John Silver and the crew are pirates, but the crew don't know that their secret is out.
Squire Trelawney and Captain Smollett ambush Israel Hands and five other sailors on board the Hispaniola; open war breaks out against the pirates.
Once the Hispaniola arrives at Treasure Island, the uneasy truce between the pirates and the good guys seems set to fall apart. The good guys know that the pirates will make their move any minute, so they decide to get the drop on them. In Chapter 16, Captain Smollett gives two-thirds of the crew shore leave, and they head off happily. Then Captain Smollett and Squire Trelawney ambush the remaining sailors aboard the ship and lock them up. Meanwhile, Doctor Livesey goes to the island and identifies an abandoned fort with a spring of fresh water where the good guys can make their stand against the pirates. So the good guys bring their supplies from the Hispaniola to the fort; once they make their move, it's open war between the pirates and the good guys.
Jim goes off to steal the Hispaniola from the pirates while Doctor Livesey and the rest remain on the island to deal directly with Long John Silver.
We now know that the main conflict of the novel is going to be between the pirates and the good guys over the treasure. Now that it's come to open struggle between the two groups, we're just waiting to see how everything is going to be resolved. By stealing the Hispaniola from the pirates, Jim breaks their morale, causing strife within the pirate group between Long John Silver and the men he's trying to lead. When Jim accidentally becomes a pirate hostage, he finds out about this struggle and he and Long John Silver form a fragile agreement to help one another get out of this mess alive. Meanwhile, Doctor Livesey has made an agreement with the marooned man, Ben Gunn, who leads Doctor Livesey to Captain Flint's treasure. Once Doctor Livesey knows where the treasure is, he can afford to hand over the treasure map to Long John Silver, since it's not going to do Silver any good. So over the course of the ten chapters, from 22 to 33 or so, we see the twists and turns that bring Long John Silver, Jim Hawkins, and even Doctor Livesey into an alliance.
Jim Hawkins and Long John Silver find the empty treasure pit; Doctor Livesey and his men arrive to save the day.
In Chapter 33 everything comes to a head: Long John Silver leads his remaining pirate crew to the place on the map where the treasure has been buried, only to discover that it has already been dug up. Just as it looks like the pirates are going to kill both Long John Silver and his hostage Jim, Doctor Livesey arrives with Ben Gunn and a loyal sailor, Abraham Gray. They ambush the pirates and drive them into the forest. Doctor Livesey explains that it was Ben Gunn who found the treasure two months before, so Long John Silver's map has been useless all along. Now that the good guys have control of both the ship and the treasure, the pirates have no choice but to run away empty-handed.
The Hispaniola leaves Treasure Island.
All that's left at this stage is the mopping up: the good guys decide to maroon the three remaining pirates on Treasure Island with some supplies and ammunition. As they're returning to England, Long John Silver manages to slip away when they're at port. We don't know exactly what happens to him, but he's clever enough to look after himself. Ben Gunn gets the thousand pounds Doctor Livesey promised, which he spends in under three weeks. The rest of the good guys get their fair share of the treasure. So everyone lives happily ever after, though Jim still finds himself haunted by nightmares of his terrible adventures on Treasure Island.