Could you check your sources for Dexters? I have several who were "last seen" in Knox County.
Hiram Dexter, wife Almedia [aka Almada], children Henry & Louise, Berlin Twp, 1850.
His sister, Mary Dexter, Fredericktown, 1860.
"The History of Knox County, Ohio. Its Past and Present" lists their father, Delano Dexter, among charter members of Thrall Lodge, Fredericktown, 1849. Neither he or his wife, Olive, have been found on any 1850 census.
A son-in-law, Hubbard Thompson, also could have died in Knox County [before 1850 when his wife Lydia living with in Fredericktown with her sister Mary].
Two other sons, Antipas & Chauncey Dexter, and their familes also lived in Knox County but had moved on to Morrow.