"Spaceships in thousands, and they're attacking us! They've come from
somewhere toward our galaxy--have come out of intergalactic space itself
to attack our universe!"
The interstellar Patrol, that fabulous fleet manned by all the assorted
races of our galaxy, faced its greatest struggle when that alarm came
through. For this was an attack from Outside the Universe, a vast
migration from another galaxy, and it had to be stopped if a thousand
worlds were to survive!
This terrific classic space novel on the grandest scale involves three
giant galaxies in an all-out conflict.