What Happened to Book of Mormon Witnesses?

The names of Oliver Cowdery, David Whitmer, and Martin Harris are familiar to most of us, notably because of their role as witnesses to the reality of the Book of Mormon. (Note: the three witnesses, unlike the eight witnesses, were shown the plates by a heavenly messenger, not Joseph Smith.) But though their testimonies are still printed in the beginning of every copy of the Book of Mormon, all three of these men left the Church at some point—only two returned. Find out what happened to the three witnesses after they signed their names to their testimonies.