Worlds of the Imperium

Brion Bayard, an American diplomat assigned to Stockholm attempts to evade men he believes to be Soviet agents, only to find himself kidnapped by agents of the Imperium from a parallel world. Taken to their homeworld, he's introduced to the aristocrats of the government, which rules most of the civilized world from London, having been formed by the union of the British, including America, German & Austro-Hungarian empires. He's impressed by the commitment to duty of the officials he meets & drawn to a noble lady. The main reason for his abduction is that the Imperium is under attack from another parallel world. The Maxoni-Cocini drive, a technology for traveling between worlds, is dangerous. Almost all worlds where its development is attempted are destroyed horribly. The collection of timelines where this occurs is known as the Blight. The rare ones where Earth survives are known as Blight Insulars. BI-1 is the Imperium. BI-3 is Bayard's world, where the technology never developed. The raids are coming from BI-2, a chaotic world where war has swept the planet for generations & which wasn't believed to have the drive. It's ruled by a dictator, who happens to be Brion Bayard. Bayard trains to substitute for his double, presumably after killing him, & take over the other government, shutting off the raids. The plan falls thru almost as soon as he arrives in the new world. For some reason, nobody believes his impersonation. The reason becomes apparent when he meets the other Bayard, who lost both legs in battle years before, but who's concealed the fact from the public. This other Bayard isn't the evil dictator he's portrayed to be. He greets his double as a brother & tells him how he became dictator to pacify his world. He knows nothing of the raids on the Imperium. The two Bayards talk over a meal, discovering they've much in common. Bayard the dictator is assassinated by conspirators, who are working for power-hungry factions in the Imperium itself, using stolen technology. Bayard himself is scheduled for execution, after suitable amputation surgery, to allow the conspiracy to consolidate its hold by publicly eliminating the dictator...