Stephen Fry and zoologist Mark Carwardine set out to discover how the lugubrious Amazonian manatee, a freshwater mammal, has survived the last two decades, but Stephen breaks his arm deep in the Amazon rainforest.

On a journey across Africa towards the war-torn Congo, the travellers encounter chimpanzees, gorillas and elephants, but are there any northern white rhinos still alive in the wild? The news is not good but there is some hope in the remarkable project under way to save the black rhino in Kenya.

In Madagascar the travellers encounter the biggest and the smallest lemurs on earth. But they are searching for the aye-aye, a peculiar lemur which, according to local legend, brings death to those who encounter it.

In a dramatic conclusion to the series, the travelers have a close encounter with grey whales and meet the deadly Humboldt squid in a search for the mighty blue whale, the biggest creature that has ever lived.