Mention personal revelation, and responses can range from conversion to the choice of an airline seat. But what happens when personal revelation directs a Mormon polygamist to take the life of his sister-in-law and her infant daughter? And what might Joseph Smith and Brigham Young have to do with it? In his best-selling book Under the Banner of Heaven, author Jon Krakauer suggests these murders would not have occurred outside the unique history and doctrinal framework of Mormonism.