Investigating a huge, strange spacecraft, Commodore Rex Clive and Adjutant Speed Lansing of the Space Rangers encounter a space-suited figure in the darkness. The figure's "solidium" armor makes him immmume to their "sun-bolt" pistols. The figure uses a "gravigun" on the lawmen. The weapon places Rex and Speed into a state of unconsciousness. they awaken to discover the ship is run by Erda, leader of a galactic expedition from the planet Dox. Erda reveals the figure's name is Dav, her bodyguard.