A crime has occurred in a bucolic corner of Washington State so ghastly it is hard to believe it actually occurred. Exactly what crime took place is elusive, but Attorney General Janet Reno has a duty to find out. The small town of Wenatchee was the site of either a massive sex ring involving the ritualistic rape of dozens of children or a police witch hunt that has imprisoned dozens of innocent people, wrongly torn children from their parents and destroyed the reputations of upstanding citizens who dared to question authorities. Whatever happened, the truth must come out and only federal investigators have the objectivity and experience to find it. Such a step would be a highly unusual intrusion into a local law enforcement matter. But what happened in Wenatchee has implications for the rest of the country, for if this could happen in quiet Wenatchee, with the resolute backing of prominent local officials, it could happen anywhere. The quick acquittal Monday of a lay minister and his wife on charges that they were the leaders of this bizarre sex ring whose victims included their own 5-year-old daughter and whose crime sometimes occurred before the altar of their own church, ought to be enough to persuade Reno to conduct a thorough investigation. Robert and Connie Roberson had the advantage of a private attorney, who tore into the state's shaky evidence. No physical evidence was ever presented. Prosecutors relied on the testimony of children and a single adult, a convicted child rapist whose own charges of rape were reduced to misdemeanors in return for his testimony. The Robersons were acquitted, but only after spending four months behind bars and _ the worst nightmare of all _ losing their daughter to the state. They now have to go to court to regain custody. Their troubles appear to be rooted in their own public criticism of the investigation. They were arrested two months after speaking out. In a troubling pattern, not one defendant who has hired a private attorney and fought the charges has gone to prison. Most of the convictions have been the result of plea bargains, and many of the guilty have been described as "developmentally disadvantaged." There have been allegations of police intimidation during the investigation. The driving force behind the investigations was a police detective, Robert Perez, who never taped a single interview, routinely destroyed any notes he made and relied primarily on the testimony of a troubled 13-year-old girl _ his own foster daughter. Even the harshest critics of Perez acknowledge that there may have been some cases of sexual abuse. But the investigation appears to have spun out of control by an overzealous, inexperienced and unsupervised investigator. One of the most troubling aspects of the case is the heavy reliance by prosecutors on the testimony of children elicited through so-called recovered memory sessions by therapists. This questionable technique has been widely repudiated for creating false memories that lead to false testimony. So many questions have been raised by this investigation that Washington Gov. Mike Lowry has called on Reno to investigate. She reportedly is reluctant to do so because of the cloud it would place over local authorities. But that cloud already is there, darkening the lives of innocent people. Reno owes it to Wenatchee and the rest of the country to find out what really happened there.