Bracing finale to Vallee's ``Alien Contact trilogy'' (Dimensions, 1988; Confrontations, 1990), as the ufologist brings some famous UFO cases down to earth--and into the mud. In Dimensions, Vallee presented his theory that UFOs are probably not spacecraft but manifestations of a consciousness- controlling ``technology'' from ``dimensions beyond spacetime''; in Confrontations, he bolstered that theory with examples from his own casebook. Here, deftly blending theory and memoir, he attempts to clear ufololgy of ``the weeds and the vines of human fantasy and...the poisonous flowers of unbalanced minds.'' That is, to Vallee, cases from the infamous Roswell incident (spacecraft and aliens purportedly captured by the US Army in 1947) to the popular legend of Area 51 (aliens working tentacle-in-hand with US officials beneath the Nevada desert) to the alleged abduction of Franck Fontaine in 1979 (exhaustively researched firsthand by Vallee) to the purported top-secret federal UFO-investigating committee of Howard Blum's Out There (1990) are not only mostly nonsense, but--here's the rub--``complex hoaxes that have been carefully engineered for our benefit.'' But by whom, and why? By federal disinformation agents, and possibly as ``psychological warfare experiments'' or ``as a cover for something else''--i.e., experimental spy/warcraft or real ``flying discs.'' Vallee offers little hard evidence to back those conjectures, but he does unglove the heavy hand of military intelligence in many cases, while at the same time exposing the absurdity of others, including Budd Hopkins's best-selling alien-rape reports. So what's left? A host of genuinely mysterious cases, e.g., the 1989 Soviet Union sightings, and the spirit of rigorous scientific inquiry that Vallee urges they be subjected to. Except for Vallee's wobbly conclusions, a forceful and refreshingly iconoclastic study that, for all its good sense, will likely add up to only a cry in the alien-infested ufowilderness.