Over the course of a single night filled with cat-and-mouse intrigue, a young boy thwarts the efforts of a Yevd espionage ring to infiltrate a vast military spaceship-construction yard.
The Yevd are aware of this, and have repeatedly tried to infiltrate the Yard, the massive industrial zone at the center of Solar City where the Ship is being built, but humans have successfully kept them out with air barriers which circulate an assortment of microbes lethal to the aliens.
Unlike the Yevds, who hailed from the Milky Way, had exchanged ambassadors with humans, and were engaged in a relatively low-intensity territorial war, the Rulls were an implacably hostile extra-galactic species bent on exterminating all other intelligent life.
The two races were also physically quite unlike each other; the Rulls were described as bone-white, muscular, carnivorous worm-like beings who ambulated with the aid of with numerous suckers (which also served as mouths), and who fed by paralyzing large prey (including humans) before burrowing into the body cavity and consuming the victim from the inside.
By contrast, the Yevd were described as a tall, angular, and black, with many piston-like reticulated arms and legs and the ability to communicate via modulated light, project holographic disguises, and fire energy blasts.
A 1952 review of Destination: Universe in Galaxy Science Fiction, mostly positive despite finding fault with the "coldness of [van Vogt's] writing and the woodenness of his characterizations," briefly dismissed the story as "not tops".