The book by the famous American researcher of the unknown, Ivan Sanderson, talks about a variety of manifestations of an unknown reality that has not yet found an explanation in science. Unknown monsters of the seas and oceans - giant eels, humanoid creatures of the jungle and northern forests, giants and dwarfs - these are just some of the characters that concern Sanderson the zoologist. In addition, he explores mysterious luminous circles in the ocean, cases of UFO manifestations, issues of teleportation, and other aspects of parapsychology.