A Starfleet officer and old crewmate of La Forge who began transforming into an alien species after a mission to Tarchannen III.
Lieutenant Commander Susanna Leijten served with Geordi La Forge on the USS Victory, where both took part in an away mission to Tarchannen III. Years later she learns that every other member of that team has deserted and tried to return to the planet.
In Identity Crisis, Leijten comes aboard the Enterprise and soon begins mutating into one of Tarchannen III's native beings, as does La Forge. Dr. Crusher finds a way to reverse the change in her, and Leijten then helps coax the transformed La Forge back so that he can be cured as well.