Did celebrated outlaw Butch Cassidy perish in a blaze of gunfire at the hands of the Bolivian rurales? Or did he return to the States and live as William Phillips, a respectable Spokane businessman and inventor? Pointer, an amateur historian of the West, follows a dusty trail with the tenacity of an Indian scout, sifting the reports of pro and con factions among Cassidy's many admirers and checking the oral testaments of the citizens of Wyoming (including Butch's still-living sister) whom Cassidy is alleged to have visited in the 1930s. He concludes that the truth or falsity of the ""Cassidy lives!"" rumor depends on a manuscript, William Phillips' ""Bandit Invincible,"" in which Phillips detailed his ""friend"" Cassidy's criminal career to set the record straight. Ahem! Among Phillips' claims for his buddy: ""I am happy to say that I have never known a more courageous and kinder hearted man"" and ""his reputation for veracity and integrity in all his dealings, aside from holdups, is unquestioned."" Checking the mss., the author vouchsafes, ""involved thousands of miles of travel,"" the testimony of a handwriting expert, and the corroboration of numerous holdup details. In the event, the quest was not in vain for Pointer can now avow that Cassidy's exploits included prospecting in Alaska and riding with Pancho Villa in Mexico! Will this lay the Butch Cassidy controversy to rest? Don't bet your ten-gallon hat, your trusty pony, or your last silver dollar.