On the east side of the island, rugged mountains rise dramatically from the palm fringed Indian Ocean. These uplands catch drenching rains almost all year round - steep and inaccessible, they are the most diverse part of the island. "Lost Worlds" travels from the highest mountains, where trees are few and it's cold enough for frost, through the lush, cloaking rainforests, down to the tropical coast, discovering the ringtailed lemurs, the jeweled geckos and the predatory wasps. So what is it that has made this narrow eastern strip in particular so rich in life?