The Voltarians come to the conclusion that the indigenous inhabitants of Earth will destroy the planet through pollution and possibly war, which would disrupt the future of their invasion timetable.

Royal Combat Engineer Jettero Heller, a character of perfection, incorruptibility, and astonishing ability, is assigned to save Earth from the Earthlings.

Heller's attempts to break the demonic control of Earth by Rockecenter make him a target, and the corporation uses its most dangerous weapons to destroy him: psychiatry and psychology, and a mad, idealistic public relations genius by the name of J. Walter Madison, aka J. Warbler Madman.

After a series of world-shattering events, which include the impact of an ice meteor on the Soviet Union, the world's entire oil supply being turned radioactive, and a black hole orbiting the Earth, Heller returns to Voltar to find that not only have Hisst's plans to enslave the government nearly succeeded, but Madison is starting a galactic civil war.

The Encyclopedia of Science Fiction describes the series "whose farcical overemphases fail to disguise an overblown tale that would have been more at home in the dawn of pulp magazines".

[3] The New York Times review of the first volume, The Invaders Plan, describes it thus: "... a paralyzingly slow-moving adventure enlivened by interludes of kinky sex, sendups of effeminate homosexuals and a disregard of conventional grammar so global as to suggest a satire on the possibility of communication through language".

[4] In L. Ron Hubbard and Scientology, a survey of Hubbard's literary career, Marco Frenschkowski of the Johannes Gutenberg University of Mainz described the Mission Earth series:[5] In 1991, the town of Dalton, Georgia attempted to remove the Mission Earth books from its public library, citing what was described as "repeated passages involving chronic masochism, child abuse, homosexuality, necromancy, bloody murder, and other things that are anti-social, perverted, and anti-everything".