Mac Tonnies' book "Cryptoterrestrials: A Meditation on Indigenous Humanoids and the Aliens Among Us" makes the case that the UFO phenomenon is terrestrial in origin. Tonnies' book posits a breakaway humanoid civilization operating parallel to humanity. The cryptoterrestrials are dependent on us for genetic material, but fear us as an existential threat. They kidnap humans for the material required to replenish their gene pool, while spinning an elaborate and fantastical story of their off-world origins. According to Tonnies, cryptoterrestrials are a better explanation for UFOs and other paranormal phenomena than the more popular extraterrestrial hypothesis, because they explain the nonsensical dimensions of UFO encounters as part of the cryptoterrestrial deception program.

Dane outlines Tonnies' arguments in favor of cryptoterrestrials and critiques the idea before making the case that the cryptoterrestrial theory advances UFOlogy by reintroducing the potential role of systematic deception in understanding UFOs and paranormal phenomena.