How does Jim Hawkins learn about the crew plan to mutiny?

Jim Hawkins learns about the crew's plan to mutiny when he overhears a conversation between some of the ship's crew members in the stockade. They discuss their intentions to seize control of the ship and eliminate the loyal crew. This revelation instills a sense of urgency in Jim, prompting him to warn Captain Smollett and his allies about the impending threat. His eavesdropping ultimately sets the stage for the unfolding conflict between the loyalists and the mutineers.