A classic novel by Eric Frank Russell first published in Unknown in 1939.
Famous scientists start suiciding and the main character slowly discovers that they have all treated themselves with an odd combination of chemicals, and that something they see after the treatment drives them to insanity or suicide. He treats himself, and discovers that new can now see gaseous blobs — Vitons — which appear to be feeding off human emotion. Apparently intelligent, they seem to be milking humanity and controlling it to produce the maximum of emotion, causing wars and other evils.
He starts spreading the word and is immediately being chased by the Vitons. As more and more people become aware of them, the Vitons switch from herding to extermination, and in an all-out war, humanity is — barely — the victor.
Sinister Barrier is a novel based on Charles Fort's idea that "men are cattle" of seem unknown advanced race. See also Forteanism.
