At 4.6 billion years old, the Solar System is our solid, secure home in the Universe. But how did it come to be? In this episode we trace the system's birth from a thin cloud of dust and gas. Shocked by a nearby supernova, the pull of gravity and natural rotation spun it into a flat disc from which the Sun and planets coalesced. It all happened in the space of 700 million years, during which the planets jockeyed for position, dodging the Late Heavy Bombardment of deadly asteroids and setting into the neat, stable system that we now realize might be a rarity in the universe.

There are 200 million insects for each of us. They are the most successful animal group ever. Their key is an armoured covering that takes on almost any shape. Darwin's stag beetle fights in the tree tops with huge curved jaws. The camera flies with millions of monarch butterflies which migrate 2000 miles, navigating by the sun. Super slow motion shows a bombardier beetle firing boiling liquid at enemies through a rotating nozzle. A honey bee army stings a raiding bear into submission. Grass cutter ants march like a Roman army, harvesting grass they cannot actually eat. They cultivate a fungus that breaks the grass down for them. Their giant colony is the closest thing in nature to the complexity of a human city.

Sultan Mehmed II's siege of Constantinople enters its third week. Mehmed's artillery teams continue their relentless bombardment of Constantinople's walls. After his navy suffers a devastating defeat, Mehmed moves his ships overland to the Golden Horn in a daring, visionary feat. In the shadow of betrayal, Giustiniani attacks the Ottoman fleet.

Michelle McNamara reflects on the 1984 murder of her childhood neighbour Kathy Lombardo, which she credits with planting the seed for her lifelong fascination with unsolved crimes. Michelle really wanted this child and wished to get her murderer caught. The story of the victims has to be told.

Dave Grohl returns to his musical roots, while the Foo Fighters prepare to record at Seattle's Robert Lang Studio with Death Cab for Cutie's Benjamin Gibbard. Dave sets his focus on the Seattle music scene, mainly the grunge movement and its implications in American Rock Music. Interviews with Chris Cornell, Nancy Wilson, Bruce Pavitt.

Jessie Buckley narrates the extraordinary story of the first transatlantic communications cable. In 16 August 1858, a short message is telegraphed from County Kerry to Newfoundland, 3,000km away: ‘Europe and America are united by telegraph. Glory to God in the highest, on earth peace, good will towards men.’ The Morse code message is conducted along the new underwater transatlantic telegraph cable laid across the bed of the Atlantic Ocean. Sending the same message by ship would have taken at least ten days, but the transmission takes just hours and heralds the dawn of the modern communications age.
The quest is driven by visionaries and pioneers. Among them are Cyrus Field, a wealthy businessman who, despite his immense success, ends his life in poverty; Samuel Morse, inventor of the telegraph and Morse code; Isambard Kingdom Brunel, the British engineer who pushes boundaries and budgets; and Belfast physicist Lord Kelvin, who calculates how to achieve what had hitherto been deemed impossible. Together, their ingenuity and relentless pursuit helps realise one of the great scientific accomplishments of their age for which Valentia, on Ireland’s remote western coast, is ground zero.