Fathom is a visual and aural wonder of a documentary that follows researchers working to finally decode the communication of humpback whales. Dr. Ellen Garland and Dr. Michelle Fournet embark on parallel journeys on opposite sides of the world, as they seek to better understand whale culture and communication. The film uniquely reveals a deep commitment and reverence to the scientific process and the universal human need to seek answers about the world around us.
From hypothesis to groundbreaking experiences in the field, 'Fathom' showcases the passion, curiosity, collaboration, perseverance and work it takes for leading scientists to make scientific discoveries.

The French army stops the German advance at the battle of the Marne, while the Germans halt the Russians at Tannenberg on the eastern front. In France, the warring parties dig themselves in for 4 years in the trenches. Soldiers from the colonies come lend a hand to their colonizers and the war becomes global.

In a late Jurassic forest in what is now China, an Epidexipteryx escapes from a juvenile Sinraptor by climbing a tree. It finds a beetle grub in the tree bark, being shown to use its elongated fingers in a similar way to a modern day aye-aye. However, its prey is stolen by another, larger Epidexipteryx, and after a brief bout of posturing, the smaller individual goes to find more food. It drops a second grub to the forest floor, where the other Epidexipteryx retrieves it, only to be killed by the juvenile Sinraptor. The episode then cuts to a desert in late Cretaceous Mongolia, where a Saurornithoides is shown brooding a nest of eggs. When it leaves the nest, an Oviraptor raids it, fleeing when the troodontid returns. The Saurornithoides is suddenly attacked and eaten by a Gigantoraptor, which then heads to compete in a breeding ritual for mates. The males use their feathers for display, a brief fight between two erupting at one point, allowing the females to choose the best suitor. The episode finally cuts to an early Cretaceous forest in China, where a Xianglong is being hunted by a Microraptor, which uses its feathers to pursue the gliding lizard in the air. A Sinornithosaurus attacks it, and after a brief chase the Microraptor manages a lucky escape. The Sinornithosaurus, alongside two other members of its species is then shown hunting a Jeholosaurus and its three young. The group brings down the parent, the narrator explaining that their possibly venomous bite allowed them to tackle animals much larger than themselves. A montage is then shown of the feathered dinosaurs featured in the programme, with the narrator saying that Microraptor not only hints at how flight might have developed, but also that dinosaurs still live amongst us today, as birds.

In the fifth episode of the series, lavish imperial games at the Colosseum are highlighted by the emperor's bloody victories, but his paranoid abuses of power lead to a final betrayal.

Dr Iain Stewart investigates the counter-attack that was launched by the global warming sceptics in the 1990s. At the start of the 1990s it seemed the world was united. At the Rio Earth summit the world signed up to a programme of action to start tackling climate change. Even George Bush was there. But the consensus didn't last.
Iain examines the scientific arguments that developed as the global warming sceptics took on the climate change consensus. The sceptics attacked almost everything that scientists held to be true. They argued that the planet wasn't warming up, that even if it was it was nothing unusual, and certainly whatever was happening to the climate was nothing to do with human emissions of greenhouse gases. Iain interviews some of the key global warming sceptics, and discovers how their positions have changed over time.

Could the fabled lost city of Atlantis have been located? Professor Freund explained how he led a pursuit to find the lost civilisation, believed by many to be an ancient Greek myth, by using deep-ground radar, digital mapping and satellite imagery. He contends that Atlantis, described by Plato in 360BC, in Spain's Donaña National Park, north of Cadiz, and was wiped out by a giant tsunami. Plato wrote it had been destroyed by a natural disaster in 9,000BC. Experts are now surveying marshlands in Spain to look for proof of the ancient city.