Their first contact with other people comes after several months when they observe two large outrigger canoes land on the beach. The two groups are engaged in battle and the three boys intervene to successfully defeat the attacking party, earning the gratitude of the chief Tararo. The Polynesians leave and the three boys are alone once more.
Then more unwelcome visitors arrive in the shape of pirates, who make a living trading, or stealing, sandalwood. The three boys conceal themselves in a hidden cave, but Ralph is captured when he sets out to see if the pirates have left, and is taken aboard the pirate schooner. Ralph strikes up an unexpected friendship with one of the pirates, "Bloody Bill", and when they call at an island to trade for more wood he meets Tararo again. On the island he sees all facets of island life, including the popular sport of surfing, as well as the practice of infanticide and cannibalism.
Rising tension leads to an attack by the inhabitants on the pirates, leaving only Ralph alive and Bloody Bill mortally wounded. However they manage to make their escape in the schooner. After Bill dies, making a death-bed repentance for his evil life, Ralph manages to sail back to the Coral Island to be re-united with his friends.
The three boys sail to the island of Mango where a missionary has converted part of the population to Christianity. The boys find themselves in the middle of a conflict between the converted and non-converted islanders, and attempting to intervene are made prisoners. They are only released a month later after the arrival of another missionary, and the conversion of the remaining islanders. The 'false Gods' of Mango are consigned to the flames. The boys then set sail for home, older and wiser.