Having finally concluded that they are not alone on the island, the eight castaways try to piece together evidence that will help them identify the other inhabitants.

The castaways spot a boat heading toward the island. They want to stay hidden. Mandrill and his Hanuman guards want to force the castaways out of hiding so that they will be recaptured and taken away from the island. Whose plan will succeed?

The castaways split into pairs to search for the Hidden Valley and its promise of plentiful food. Each of their paths may lead to the same place, but each has its own dangers. Will their new acquaintance Spider help them to safety, or betray them?

Despite Bushbaby's misgivings, the young castaways befriend the spider monkey that was stealing their food, especially after he promises to give them information about the hidden rulers of the island.

Determined to find the mysterious mountain that seems to appear and disappear from view, the castaway monkeys use all their skills to orient themselves in their search, unaware of the dangers surrounding them as they move into the forbidden territory of the Tamarin kings, the secret rulers of the island.

The Emperor is ready to reveal the island's secrets to Bushbaby. What he tells her is almost impossible for her to believe. Perhaps there is more to the Emperor-and the island-than meets the eye?

A storm comes to the island. The castaways must work together to prepare for it-and to help a fallen Hanuman guard. Choices must be made. What is the probability that the castaways will uncover more of the island's secrets?