For the past six years, the road to Bill Clinton has often run through Douglas Band, a 34-year-old former White House intern who has helped manage Mr. Clinton's time, accompanied him around the world and even fielded some of his calls. Two years ago, Mr. Band befriended a handsome and charming Italian businessman named Raffaello Follieri. The young Italian, now 29 years old, had moved to New York in 2003 to launch a business buying and redeveloping Roman Catholic Church properties. He claimed close ties with Vatican officials that would smooth the way for deals, according to business associates and...