Children of the Lens — E.E. "Doc" Smith

The ultimate weapon

It was beginning to look as if no one could prevent the destruction of the Universe. For a strange intelligence was directing the destruction of all civilization from the icy depths of space.

Kim Kinnison of the Patrol was one of the few men who knew how near the end was. And in the last desperate plan to save all life, he knew he had to use his children as bait as the evil powers of the planet Ploor.