Book One of this volume recounts the mystery of the arrival on Earth of a space ship from a distant planet, bringing strange creatures whose tremendous knowledge has made possible travel across the star-ocean. When the interplanetary ship, which had buried itself deep into the desert sands of Arizona, is recovered by the tireless work of engineers, Professor Brandon discovers inside the space vessel the Stellarites, encased in containers in a state of suspended animation. Here then is the secret of space travel...but can our scientists untangle the mystery of suspended animation? In attempting this, Dr. Farrington, the leading medical authority, places his own son in the death-like state but finds he cannot release either his son or the Stellarites from the mantle of sleep. A further complication is the discovery of parchment writings in the Stellar Missile telling the purpose of the visit.

Book Two tells of the Second Missile hidden in the frozen wastes of Siberia. Armed with greater knowledge, gleaned from the fifteen years of work during the period of the discovery of the First Missile and the finding of the Second Missile, an expedition of American scientists invades the Russian wilderness to the Missile site. Determined to bring the sleeping Stellarites back to America for security reasons, the scientists are terrified to learn that the Siberian Missile contains living creatures, and these powerful, intelligent humans are preparing to rescue their companions from the first space ship.