In 2267, Marple was part of a nine-man landing party that was assigned to survey the planet Gamma Trianguli VI. Shortly after arriving on the planets surface, Marple was attacked and killed by the Feeders of Vaal, at the order of their controlling computer, Vaal. (TOS episode: "The Apple"; TOS - Crucible novel: The Star to Every Wandering)
- It is unclear if Marple was killed or merely injured in the attack in "The Apple". However in The Star to Every Wandering, Kirk revisits the mission to Gamma Trianguli VI while in the Nexus and convinces himself not to intervene as "no matter if Hendorf and Kaplan, Mallory and Marple survived", they still wouldn't be saved in the real universe.