An extremely frail, old-looking man living on the planet Arret in the antimatter universe discovered by the crew of the U.S.S. Enterprise on stardate 6770.3 (2270). Karl Four was actually the son of Karla Five, a woman who appeared to be several decades his junior. The backward flow of time in the antimatter universe accounted for this apparent paradox. Karl Four provided invaluable assistance in getting the Enterprise and her crew back home from the antimatter universe.