The octopus is a close cousin of the oyster and snail. And yet, even by human standards the multi-limbed creature is considered highly intelligent. In this Nature of Things documentary, scientists from around the world test the formidable brain power of this brilliant creature and reveal some very human traits. The octopus exhibits curiosity, cognitive reasoning and abstract thinking. Just how has an animal that is so different from humans become so intelligent? Through fascinating experiments in the lab and in the wild, follow scientists in their efforts to understand how the octopus has evolved.