What if...there is more than one Earth? Sister worlds exist, recognizably alike yet startlingly different. And the "gate house" between these worlds is a closely guarded secret of America's fanatical leader... - For President Robinson, the gate house is a military ace-in-the-hole, a last laugh in his ever-more aggressive sparring with the Soviets. - For Senator Endicott, the first man to travel from one Earth to another, the Alternities provide a playground for his most…