In 2266, Nellis was served as navigator and first officer aboard the Federation science vessel Antares, under the command of Captain Ramart. In this year, the Antares discovered Charles Evans, a 17-year-old survivor of a crash on the planet Thasus. Shortly after, the Antares rendezvoused with the USS Enterprise, which was to continue transporting Evans to Colony 5.
Nellis died along with the rest of the crew of the Antares when they tried to warn the Enterprise that Evans possessed psychokinetic powers. Ironically, Evans used these powers to remove a warped baffle plate from the Antares's energy pile and caused a warp core breach.