Okto agent 'Min', who went on an expedition to the Amazon rain forest, feels something unusual when he sees a river that has completely disappeared. In addition, a group of cranky 'howler monkeys' who should live on the forest floor, the top of the tree, also come downstairs and recklessly try to drive out 'Min'... Hearing 'Min"s good soil warning, Octonauts dispatch to the tropical rain forest!