Earth Factor X

"Reality twisted... slightly. Earth shivered in a momentary absence of vibration. For a split second the solar system wasn't. And then was again. Less than a billionth of a second... but a time shift occurred for connected purposes. As the shadow ship started to emerge from the time jump, men and aliens were locked in a secret, undeclared war to rule Earth. The aliens, genetically changed, looked exactly like humans. They were everywhere--in government, in business, in finance. Opposed to them were two women and one isolated brain in a mechanical body. But between them they possessed the one secret that the aliens had never discerned about the people of Earth..."--Pg. [4] of cover.