Journey to secret worlds where lives are wrapped in unexpected of ways. The fifth episode of the series takes viewers into the fascinating world of forests, revealing their hidden complexities and the intricate relationships within. Initially perceived as tranquil, forests are in fact bustling with life and intricate ecological interactions. The episode showcases various species, each with its unique lifestyle and survival strategies. Highlights include the Oriental pied hornbills in Borneo, whose extraordinary nesting rituals and partner dynamics are captivating.
The Amazon rainforest is explored, introducing the peculiar treehoppers and their unique communication methods, vital for survival amidst numerous predators like ants and assassin bugs. The episode also delves into the intelligent and cooperative hunting techniques of dholes in the forests of India. The narrative takes a turn to China, focusing on the visually stunning courtship displays of Temminck's tragopans and golden pheasants. In the temperate rainforests of Western Canada, the rare spirit bear and its unique relationship with its habitat are examined.
The episode concludes with an insightful look at the impact of human activity on forests and their inhabitants, particularly focusing on chimpanzees in Uganda, whose survival is increasingly intertwined with human expansion.

David Attenborough continues his search for the origins of flying animals, as he charts the rise of new, larger creatures – extinct reptiles that flew on wings of skin, dinosaurs that sprouted feathers to become the ancestors of birds, and gliding mammals that emerged from a life in the trees to dominate the night as bats. His journey spans the globe – from the rainforests of Borneo to see bizarre gliding animals, to China and its new discoveries of dinosaur fossils. Stunning CGI brings to life creatures that disappeared over 200 million years ago, and new filming techniques bring us closer than ever to the secrets of flight itself.

Dr Alice Roberts looks at our ancestors' seemingly impossible journey to Australia. Miraculously preserved footprints and very old human fossils buried in the outback suggest a mystery: that humans reached Australia almost before anywhere else. How could they have travelled so far from Africa, crossing the open sea on the way, and do it thousands of years before they made it to Europe? The evidence trail is faint and difficult to pick up, but Alice takes on the challenge. In India, new discoveries among the debris of a super volcano hint that our species started the journey much earlier than previously thought, while in Malaysia, genetics points to an ancient trail still detectable in the DNA of tribes today. Alice travels deep into the Asian rainforests in search of the first cavemen of Borneo and tests out a Stone Age raft to see whether sea travel would have been possible thousands of years ago, before coming to a powerful conclusion.

David Attenborough concludes his epic history of the evolution of flight with an exploration of the highly advanced fliers that dominate our skies today – the extraordinarily diverse skills of the birds, and the sonar-guided precision of the bats. He encounters some of our planet’s most remarkable fliers – from peregrine falcons dive-bombing starlings over Rome, to hummingbirds hovering in the cloud forests of Ecuador. In a spectacular finale, he visits Gomantong cave in Borneo to witness the mass exodus of a million bats.