In six weeks time, between July and August 1975, 27 patients at the Veterans Administration hospital in Ann Arbor, Michigan, were stricken with respiratory arrests that left them unable to breathe without mechanical aid. Some patients suffered more than one attack, eleven dying by the time physicians realized the incidents were inexplicable as natural phenomena. Investigation showed that 18 of the patients -- nine of them deceased -- had received unprescribed doses of Pavulon, a synthetic form of curare sometimes used by anesthetists as a muscle relaxant. Federal agents summoned to investigate the case reported that most of the respiratory arrests occurred in the hospital's intensive-care unit, during the afternoon shift. All the victims had been fed intravenously, and agents concluded that Pavulon was pumped directly into the feeding tubes, since injection in the larger IV bottles would effectively dilute the dosage. Examination of relevant work schedules focused suspicion on two Filipino nurses, 31-year-old Leonora Perez and 29-year-old Filipina Narciso. Both denied involvement in the crimes, but Perez was fingered by survivor Richard Neely, 61, as the nurse who entered his room -- and then ran away -- when he called out for help in the midst of a near-fatal respiratory arrest. Indicted on five counts of murder, nurses Perez and Narciso were convicted in July 1977, their verdicts overturned on appeal five months later. Charges were dismissed against the pair in February 1978, and no new suspects have been named, despite the government's insistence that at least five patients -- and perhaps eleven -- were deliberately murdered by an unknown member of the VA staff. No motive was suggested in the case, and it, like the identity of the elusive murderer, remains a mystery today.