At first, officials at the U.S. Indian Health Service overlooked the peculiarities of their unmarried new doctor. They desperately needed a pediatrician at their hospital in Browning, Mont. By 1995, after three years, they became convinced Stanley Patrick Weber was a pedophile and pushed for his removal from the government-run hospital. But the Indian Health Service didn't fire Mr. Weber. Instead, it transferred him to another hospital in Pine Ridge, S.D. He continued treating Native American children there for another 21 years, leaving behind a trail of sexual-assault allegations. An investigation by The Wall Street Journal and the PBS series Frontline found the IHS repeatedly missed or ignored warning signs, tried to silence whistleblowers and allowed Mr. Weber to continue treating children despite the suspicions of colleagues up and down the chain of command. The agency tolerated a number of problem doctors because it was desperate for medical staff, and ... managers there believed they might face retaliation if they followed up on suspicions of abuse. Mr. Weber ... was convicted in September of sexually assaulting two Montana boys ... and sentenced to 18 years in prison. He faces another federal trial later this year in Rapid City, S.D. He lost his medical license. He and his lawyers declined to comment for this article. The IHS provides medical care for 2.3 million Native Americans, many of whom have no other access to health care.