From the dean of ufologists, an instructive casebook of his own UFO investigations. In Dimensions (1988), Vallee offered his basic UFO theory: that UFOs are not interstellar craft, but are unexplained consciousness-controlling mechanisms intruding from other dimensions. Here, he expands on that theory by reference to the cases he's explored during the past three decades, concluding that ""UFOs represent a technology capable of harmful actions""--hence this book's provocative title rather than Whitley Strieber's more pacific Communion or Transformation. Before Vallee details cases of UFO hostility, however, in order to erect a scientific framework for his findings he sifts through cases that offer hard if inconclusive evidence about UFOs (sightings that have permitted readings of UFO megawatt output; manifestations that have left odd physical remnants in their wake), analyzes various UFO photos, and reflects upon the ambiguous nature of UFO research. These discussions feature copious advice and suggested guidelines for fellow UFO researchers; of more interest to general readers will be Vallee's in-depth account of his 1988 trip into the Amazon jungle to look into mass UFO sightings that involved ""medical injuries,""including deaths--e.g., that of hunter Raimundo Souza, allegedly seen by his companion to be caught in a UFO's beam, then found dead on the ground, his body covered with circular purple marks. Vallee closes by presenting a series of relatively technical definitions, classifications, and rating scales for future UFO research. A sort of personal appendix to Dimensions, partly slanted toward UFO investigators; and, as such, of limited appeal--although Vallee's findings and speculations are a core curriculum for anyone with a serious interest in ufology.