[1] The book relates Keel's accounts of his investigation into alleged sightings of a large, winged creature known as Mothman in the vicinity of Point Pleasant, West Virginia, during 1966 and 1967.

[2] It combines these accounts with his theories about UFOs and various supernatural phenomena, ultimately connecting them to the collapse of the Silver Bridge across the Ohio River on December 15, 1967.

Official investigations in 1971 determined the bridge collapse was caused by stress corrosion cracking in an eyebar in a suspension chain.

[3] Kirkus Reviews wrote that the book featured Keel's theories that "ultraterrestrials" use some form of psychic power to create hallucinations such as Mothman and UFOs.

Sherwood also reported that Keel, who was well known for writing humorous and outrageous letters to friends and associates, would not assist him in clarifying the differences.