An asocial Voyager crewman who hid on Deck 15 to pursue cosmology, until Janeway took him on a Delta Flyer mission.
Mortimer Harren is one of three crew members singled out as underperforming in Good Shepherd. Interested only in cosmological theory, he has found a remote post on Deck 15 where he can avoid others, and is openly disdainful of the mission Janeway organises for him, Tal Celes and William Telfer.
When an invisible force cripples the Delta Flyer, Harren correctly guesses it is a dark matter phenomenon, and he kills a creature against Janeway's orders. Later he tries to sacrifice himself in an escape pod to save the others, but Janeway beams him back and gets them all home.