In the far north of our planet lies the largest land habitat on earth, home to snow-covered forests and the icy open tundra. These are lands of extremes that push animals to their limits: in winter they are so cold that much of the ground has remained frozen since the last ice age. To stand any chance of survival, animals must adapt in extreme ways: here a super pack of wolves, 25 strong, has come together to take on the only large prey available to them in winter, American bison.
On the featureless tundra, an Arctic fox must strike a living alone. She is a wanderer and will roam many hundreds of miles searching for tiny lemmings, hidden deep underground. The only way to reach them is with a head dive. In the remote far east of Russia, a rare Amur leopard prowls the seemingly empty, snow-covered forest. With little prey available, it must use its ingenuity to find a meal. It follows crows in the hope of finding carrion, but it must not stay long, for it shares the forest with a far larger but equally hungry big cat, the Siberian tiger.
As spring arrives, the forests begin to thaw and life returns. Beneath the ground, a nest of tiny painted turtle hatchlings now emerge, having remained frozen in a state of suspended animation throughout winter. To the north, it is a further month before the sun’s warmth baths the frozen ground of the tundra. Tucked away underground lies a tiny snow queen – a Lapland bumble bee. She is the sole survivor of her colony - the rest perished in the winter freeze - but her larger size, her furry body and antifreeze in her blood have allowed her to survive. Now she is in a hurry. She must feed herself and raise a brood in the brief window of summer while the flowers are in bloom.
Snowy owls also use the open tundra to breed: one pair have raised a nest full of fluffy chicks. With 24-hour daylight in which to hunt, the dedicated parents bring back meal after meal for their ever-growing brood. But one day, they return to find the nest empty.
Today, the biggest challenge in the tundra is climate change. Warming summers are melting the permafrost deep within the soil, causing the ground to thaw and, in places, the land to collapse. These changes are impacting the animals too. Caribou arrive in herds of 200,000 individuals to raise their calves in the rich pastures, but warming means mosquitos emerge sooner and bother the calves before they have had a chance to gain strength. The parents drive their young to cooler, mosquito-free land, but to get there they must cross rivers running with increased meltwater and escape hungry grizzly bears. They, like much of the tundra's wildlife, are adapted to live in the extremes - but the challenge of today’s warming climate could be one extreme too many.

Be it foxes on city streets or wolves on the tundra, canines rely on sharp senses, athleticism and fierce determination to punch above their weight. But the real secret of their success is much more surprising. It's a story of their intimate side. It's what makes every dog, from pet pooch to wild dogs, one of the family.

In this captivating final episode of the series we meet some incredible conservation champions on nature's front line, fighting to preserve the future of our beautiful planet. The episode opens with a dramatic rescue operation for the critically endangered black rhino, showcasing the efforts of Dumi Zwane and his team to establish a new breeding colony in a safe haven. The focus then shifts to the Centro Jambatu research center in the Andes, where Jaime Culebras works tirelessly to save the last of certain frog species. The documentary also highlights the efforts of Trang Nguyen, who bravely infiltrates the illegal wildlife trade in West Africa to protect forest elephants from ivory poachers. Meanwhile, in Vienna, Katharina Huchler undertakes a remarkable journey to reintroduce the northern bald ibis to Europe after its extinction 400 years ago. Indigenous leader Alessandra Korap's battle to preserve the Amazon rainforest from exploitation is a key focus, alongside Mohamed Nasheed's fight against climate change to save coral reefs and his country.
This episode addresses the broader issue of habitat destruction, emphasizing its role as a primary driver of extinction. It poignantly demonstrates the interconnectivity of life on Earth and the critical importance of conservation efforts.

Deep in the jungles of Taiwan lives female giant golden orb-weaver spider -- among the biggest web building spiders on the planet. With a leg-span of almost eight inches and silk like kevlar, she's a fearsome predator. But the orb spiders must find a way to mate with her male counterparts, who are approximately 10 times smaller and 500 times lighter than she is.

Vlad Dracula presses an increasingly desperate guerrilla campaign from the shadows, hoping to demoralize the Ottomans and slow their march north. After chasing Vlad for two weeks, sultan Mehmed II and his invading army find themselves caught in a nightmare come to life deep within the Wallachian forest. Many legends have arisen out of the invasion of Wallachia in 1462. One speaks of Vlad Dracula launching a biological attack against the Ottomans to slow their march to his capital city, Târgovişte. Vlad opened his prisons and released hardened criminals to go amongst the Ottomans with tuberculosis and bubonic plague so that they could infect the enemies.
Vlad Dracula also had carried out a scorched-earth policy against Mehmed II. Along with his hit-and-run campaign from the shadows has left the sultan's troops on edge. As Mehmed's army closes on Târgovişte, tensions flare in the Ottoman camp, where food and water are in increasingly short supply. But Vlad had nowhere to rely on food for himself either and there was nowhere to go anymore. He became a prisoner of his own scorched-earth policy. Radu Dracula closes in to take Princess Anastasia hostage. Anastasia commits suicide when he reach her at Poenari castle.

In the final episode, we hear how employees on the 17th floor were rewarded, and we see Madoff's $65 billion Ponzi scheme quickly collapses as investors begin to withdraw their money during the 2008 Financial Crisis. We see how Madoff's sons attempt to stop their father from writing bonus cheques for long-time investors, faithful employees, and extended family to help cushion the blow. Madoff confesses to the Ponzi scheme, and the FBI arrests him.
After pleading guilty, Madoff is sentenced to 150 years in prison. Two years after learning of the Ponzi scheme, his eldest son Mark is found hanging from a pipe, dead of an apparent suicide. His other son dies of lymphoma six years later.