This article, originally a lecture given at Brigham Young University in 2009, was published as part of a special issue of BYU Studies featuring Thomas L. Kane. Although Kane was not a member of The Church of Jesus Christ of Latter-day Saints, he was an advocate for the Mormon cause and a trusted friend of Mormon leaders for almost forty years. Kane's legacy has been passed down in LDS memory primarily as a "friend of the Mormons" and as their "sentinel in the East." Viewing Kane exclusively through a Mormon lens, however, has obscured the rest of his life as well as his motivations for embracing the Mormon cause. Immersing Kane into his own social and cultural contexts, particularly nineteenth-century social reform, illuminates both his life and the lives of other reformers of his era.