It tells the story of seven horsemen who are sent to find why their country, a place with traits of both medieval and modern Europe, is becoming devoid of human life.

Colonel-major Silve de Pikkendorff is tasked by his margrave to go on a quest to find why human life seems to be disappearing and the City is turning into chaos.

Pikkendorff gathers six horsemen to go with him: the lieutenants Richard Tancrède and Maxime Bazin du Bourg, the brigadier Clément Vassili, the cadet Stanislas Vénier, the bishop Osmond Van Beck and the margrave’s squire Abaï.

They reach Saint-Aulick, where they meet a man named Gustavson, whose son displays a behaviour which had appeared among children in the City as a first stage of destructive events.

Kostrowitsky, who was also a famous poet greatly admired by Bazin du Bourg, had returned to the Mountain after the campaign and mysteriously disappeared.

The two remaining horsemen, Pikkendorff and Bazin du Bourg, arrive at the River at the frontier post of Sépharée, which has an unexpectedly modern bridge.