Henry Josephs 
The Fourth Invasion [EPUB ebook] 

Psychopathology has offered possible answers to why, from time to time, people in large quantities “see” strange things in the sky which manage to evade trained scientific observers, or conform to what is known about the behavior of falling or flying bodies. And mass hysteria is by no means a product of the present century. But—what if these human foibles were deliberately being exploited?