This episode details the origins of the project with fascinating background to the invention of the autochrome system, and introduces the archive's creator, Albert Kahn. It also tells the story of two incredible journeys undertaken in 1913: one by Auguste Léon to London and Cornwall, the other by the project's only female photographer, Marguerite Mespoulet, who travelled along the west coast of Ireland.

It is the eve of the First World War and Kahn's photographers are travelling from the West, where they capture the timeless values of traditional rural lives, to the East, where they witness the emerging force of nationalism – a force that would plunge Eastern Europe, and then the world, into war.

Between 1914 and 1918, Kahn dispatched several members of his team to the battlefields, where they recorded in remarkably intimate detail the everyday lives of the French troops fighting at the front. In The Soldiers' Story, viewers see them cooking their meals and even laundering their uniforms behind the front lines at The Battle of Verdun. But they also see harrowing images of death and destruction in which whole towns are razed to the ground leaving a desolate, almost lunar, landscape. Viewers witness crude medical procedures at a field hospital, and see some remarkable early shots of the aeroplanes and heavy artillery which were beginning to appear on the battlefields.

In The Civilians' Story, viewers see harrowing images of the many French towns that were razed, their churches and civic buildings destroyed to leave a desolate, almost lunar landscape. The programme witnesses some of the individual acts of quiet heroism by the nurses and doctors who tended the wounded, and sees the relief and sheer joy of the Armistice Day celebrations.