We think of comets as beautiful glowing balls of light streaking across our skies with their long sweeping tails, yet comets are so much more than just a cosmic firework display. Comets have a uniquely important place in modern science. As time machines from the early universe, they could hold the key to unlock the secrets of the cosmos. Comets could even be the origin of life itself. We follow the incredible odyssey of a comet as it sails through the solar system, watching it's every move as it evolves from a dormant chunk of ice and rock into a tumbling, violently active nucleus engulfed in a gaseous haze. What we learn is a revelation; comets are even more mysterious and fascinating than we had ever imagined.

In episode two, we discover the golden age of the La Tene Celtic warrior and reveal how their world extended as far as central Turkey. But by the middle of the first century BC, the Celts were under threat from an expanding Roman Empire, and the Gallic warrior Vercingetorix would challenge Julius Caesar in an epic battle that would shape the future of Europe.

Fifty years ago there were close to half-a-million lions in Africa. Today there are around 20,000. To make matters worse, lions, unlike elephants, which are far more numerous, have virtually no protection under government mandate or through international accords. This is the jumping-off point for a disturbing, well-researched and beautifully made cri de coeur from husband and wife team Dereck and Beverly Joubert, award-winning filmmakers from Botswana who have been Explorers-in-Residence at National Geographic for more than four years. Pointing to poaching as a primary threat while noting the lion's pride of place on the list for eco-tourists-an industry that brings in 200 billion dollars per year worldwide-the Jouberts build a solid case for both the moral duty we have to protect lions (as well as other threatened "big cats," tigers among them) and the economic sense such protection would make. And when one takes into account the fact that big cats are at the very top of the food chain-and that their elimination would wreak havoc on all species below them, causing a complete ecosystem collapse-the need takes on a supreme urgency.

Medusa was the most infamous female fiend in Greek mythology, whose look turned every living thing to stone. But what is the true story behind the snake-haired gorgon? Find out about this evil Gorgon's real world connection to human corpses and learn what clues the night sky holds concerning the origins of the tale of Medusa.

Homer's The Odyssey ranks amongst the most famous epics ever written. Follow its archetypal hero, Odysseus, as he sets sail on a twenty-year journey to return home from battle to reclaim his wife and kingdom. It's a timeless tale of adventure, filled with mythological beasts, vengeful gods, and enchanting seductresses. But could it have actually happened? Underwater divers have uncovered remains that date back thousands of years and may be a direct link to the story of Odysseus.

The story of how an eccentric French shop keeper and amateur film maker attempted to locate and befriend Banksy, only to have the artist turn the camera back on its owner with spectacular results. Billed as 'the world's first street art disaster movie' the film contains exclusive footage of Banksy, Shephard Fairey, Invader and many of the world's most infamous graffiti artists at work. No director or screenwriters are listed in "Gift Shop's" credits, just the words "A Banksy Film." Banksy is a graffiti artist with a global reputation whose work can be seen on walls from post—hurricane New Orleans to the separation barrier on the Palestinian West Bank. Fiercely guarding his anonymity to avoid prosecution, Banksy has so far resisted all attempts to be captured on film. Exit Through the Gift Shop tells the incredible true story of how an eccentric French shop keeper turned documentary maker attempted to locate and befriend Banksy, only to have the artist turn the camera back on its owner – with spectacular results. The film contains exclusive footage of Banksy, Shepard Fairey, Invader and many of the world's most infamous graffiti artists at work, on walls and in interview. As Banksy describes it, "It's basically the story of how one man set out to film the un—filmable. And failed."