In the fourth episode of the series, eyewitnesses recall how those in power at Auschwitz lined their pockets with wealth stolen from Jewish inmates while also engaging in illicit affairs.

1916. The war is raging in Europe and stretches from the trenches in France to the Italian Alps and the Balkans, and beyond to the gates of the Eastern world. The conflict becomes industrial, and millions of shells rain down on the battlefields; Verdun and the Somme are the deadliest battles in this second year of the war. Who can stop this infernal machine?

The human eye is a remarkable piece of precision engineering, but it is also extremely limited. Beyond the narrow range of light that makes up the familiar colours of the rainbow is a vast spectrum of light, entirely unseen. Richard Hammond does just that, using ground-breaking new imaging technologies to take the viewer on a breath-taking journey of discovery beyond the visible spectrum, seeing the world, quite literally, in a whole new light. From death-defying aerial repairmen in the United States using ultraviolet cameras to seek out an invisible force that lurks unseen on power lines, to German scientists unlocking the secrets of animal locomotion with the world's most powerful moving x-ray camera, to infrared cameras that can finally reveal the secrets within a humble beehive, he shows how new technologies are letting us see our world anew.

Seafood is a substantial part of the daily diet of over three billion people and oceans absorbs almost a third of all the greenhouse gases we emits. Buy the ocean it is not what it once was. Scenes of extraordinary ocean abundance now only exist in far-off places or in tales from the past. We urgently need to mend our relationship with our oceans and allow them to thrive once again.
Prince William, David Attenborough and Shakira find out about inspiring people and projects across the world that can help us stop damaging the oceans and enable their revival.

Iain explores man's relationship with fire. He begins by embarking on an extraordinary encounter with this terrifying force of nature - a walk right through the heart of a raging fire. Fire has long been our main source of energy and Iain shows how this meant that the planet played a crucial role in Britain's industrial revolution, whilst holding China's development back. Along the way he dives in a mysterious lake in Oregon, climbs a glacier of salt, crawls through an extraordinary cave in Iran and takes a therapeutic bath in crude oil.

To fly like a bird, Earthflight not only captured remarkable images of wild flocks but also relied on some extraordinary relationships between people and birds. Filmed over four years, in six continents and more than 40 countries, the Earthflight team used many extraordinary techniques. For some of the unique flying shots, members of the team became part of the flock. The birds followed wherever they went - even in a microlight over Edinburgh and London. In Africa, paragliders floated alongside wild vultures, while a model vulture carried a camera inside the flock. In South America, wild-living macaws, that were rescued as babies, still come back to visit their 'foster mother' as he travels along a jungle river. In Africa, a radio-controlled 'drone' silently infiltrates masses of pink flamingos without disturbing a feather, and microlights and helicopters capture the dramatic moment white storks arrive over Istanbul. In Africa a tame vulture carried a camera across the African bush and recreated the behaviour of his wild relatives. Similarly, in the USA, a flock of hand-reared snow geese followed the migration route of wild flocks and took in the sights and sounds of New York - managing to get lost in Brooklyn