A planet whose native life forms reproduce by converting visitors into their own species, affecting an away team from the USS Victory.
Tarchannen III is home to beings that spread by implanting a parasite that slowly rewrites a host's body into their own form. Those affected develop glowing veins, feel compelled to return to the planet and finally become nearly invisible creatures.
In Identity Crisis, the Enterprise travels to Tarchannen III after members of a former USS Victory away team steal shuttles to reach it. Susanna Leijten and Geordi La Forge, the last survivors of the group, both begin to change before Dr. Crusher can remove the infection.