- This page details Elizabeth Dehner in the primary universe; for the Elizabeth Dehner in the mirror universe see Elizabeth Dehner (mirror); for the Elizabeth Dehner in the Kelvin timeline created by Nero's temporal incursion, see Elizabeth Dehner (Kelvin timeline); for the Elizabeth Dehner in the mirror universe created by Nero's temporal incursion see Elizabeth Dehner (mirror) (Kelvin timeline); for the Elizabeth Dehner in all other alternate universes see Elizabeth Dehner (alternates).
She wrote her thesis based on herself regarding her Duke-Heidelburg Quotient and Esper abilities. This helped earn her degree in psychiatry. Dehner then worked on postgraduate studies at the Vega IV Institute, showing that some natives had esper abilities such as telekinesis, pyrokinesis and could change the weather with their minds. (TOS comic: "Who's Who in Star Trek, Issue 1")
By 2264, Dehner was in residence at the Federation colony on Aldebaran III. In early 2265, Dehner accepted a posting to the USS Enterprise, under the command of Captain James T. Kirk, for a long-term study of the affect of space duty on the human psyche (particularly in crisis situations), using the Enterprise crew as an example. (TOS novel: Strangers from the Sky, TOS comic: "Who's Who in Star Trek, Issue 1")
However, a few months after Dehner's posting to the Enterprise, the ship was ordered to patrol beyond the galactic barrier to rescue a message buoy from the SS Valiant. While breaching the barrier, Dehner and 10 other officers were effected by a strange phenomena, but only Dehner and Lieutenant Commander Gary Mitchell survived. While Dehner seemed initially unaffected by the field, Mitchell began to exhibit god-like abilities, which was discovered to be linked to the ESP ratings of the crew, with Mitchell and Dehner having the highest ratings. With Mitchell becoming more powerful and placing the Enterprise at risk, Captain Kirk decided to abandon him on Delta Vega.
While on Delta Vega, Dehner began to exhibit the same powers and freed Mitchell so they could both rule the planet. However, Captain Kirk was able to appeal to her sense of duty, and Dehner attacked Mitchell and drained his powers so Kirk could kill him. In doing this, she sacrificed her life and died on Delta Vega. (TOS episode & Star Trek 8 novelization: Where No Man Has Gone Before)