Initially, we are led to believe that these are crimes of the natural sort, until it is discovered that they were kidnapped by invisible, ethereal beings, the Sarvants, living 50,000 feet (15,000 m) above the Earth in the upper atmosphere.

[4] This is uncovered through an account found in the pocket of one of the bodies discovered, written by one of those unfortunate enough to have sojourned with Sarvants who managed to write and who chose to kill himself in order to be dumped out of their stratospheric dwelling.

After managing to capture one of the ships of the Sarvants, the French authorities discover that these enigmatic beings do not exist as individual entities, rather they are a race of tiny insectile creatures who are able to assemble and dissemble their bodies with each other in order to form temporary and functional organs controlling their machines.

[4] The Blue Peril is noteworthy due to its early anti-anthropomorphic treatment of the traditional science fiction theme regarding the possible existence of superior earthly life.

[4] The Blue Peril may have been the inspiration of other such stories about the Earth being unknowingly occupied by superior aliens, such as Eric Frank Russell's Sinister Barrier (1939).