In 2268, Horst joined Leonard McCoy and Elva Vigeland on a survey mission to an unnamed planet. The team discovered a city full of centuries-old sleeper units, most of which contained deceased humanoids. In one facility, however, Vigeland discovered one humanoid who was still alive. A monitoring robot grabbed her, and when Horst called out to McCoy, he was grabbed as well, and he was inserted into a chamber that once contained a native who'd crumbled into dust. By the time a rescue team arrived, Horst had been dead for several hours. (TOS - The New Voyages 2 short story: "Marginal Existence")
- Horst's role on the landing party was not specified.