In 2058, as humanity begins to colonize the Solar System, a gigantic black structure known as the Wall suddenly appears and cuts human territories in two. Unable to understand its nature, the United Earthes Force assigns its exploration to Purgatory Squadron, a unit made up of officers awaiting court-martial. Their mission soon draws them into a phenomenon that disrupts the laws of space and time, while tensions between military forces and powerful colonization companies escalate into open conflict. Caught in a war whose consequences extend far beyond their own era, the members of Purgatory discover that the fate of humanity may depend on the choices they make.