LDS urban legends: Cain

From the FAIR:

The notion that Cain somehow lived on, survived the Flood, and roams the earth today, is based on a single claim of David W. Patten supposedly meeting “a very strange personage,” dark and hairy, who “was a wanderer in the earth and and traveled to and fro.” (Thus managing to tie Cain to another popular urban legend: Bigfoot.)
This account was published in a biography of Patten written by Lycurgus Wilson in 1900. Wilson had a letter from Abraham Smoot giving his recollection of what Patten said. In historical parlance this is what is called a late, third-hand account—the sort of thing most historians would dismiss. This kind of testimony is simply unreliable, tainted by the passage of time and the fog of memory.
The story probably would have been forgotten if then-Elder Spencer W. Kimball hadn’t included it on pages 127–28 of The Miracle of Forgiveness. Kimball’s book has become a staple of Mormon reading, the book that many bishops give to members struggling with sin and many mission presidents assign their missionaries to read.
The passage where Kimball quotes Wilson is ... almost as a passing idea, “an interesting story” about Cain.
And so, quite innocently, Spencer W. Kimball perpetuated a Mormon myth that could (and should) have died out long ago.