At the southern edge of the Pantanal, in one of the world's largest tropical wetlands, Biologist Carolina Ribas and her local guide, Arilei Terena search for a giant otter den. Despite their large size, noisy and gregarious nature, endangered giant otters are notoriously shy and hard to find. When they find a den site that Arilei knows about it turns out to be abandoned, but it does have clues about what the otters eat.