Dexter Gray's first assignment after graduating Starfleet Academy was on a small Starfleet supply ship that ran from Federation space through the Briar Patch to the archaeological digs on Oo-oo-ah. His ship was attacked by horrible aliens (Jelly Brains, though that was not known at the time) and most of the crew including the captain were drained of life energy. Dexter's best friend from the Academy, Rico Cooper, was killed. Dexter escaped with his life only because the aliens had had their fill before they got to him.
Dexter was assigned to Banshee Squadron and flies copilot on the Banshee Squad's recon vessels and is in charge of the sensor suites, responsible for keeping everyone in the big picture. He was instantly smitten with pilot Alexandra Dalton and the two began dating. When the Squadron was forced to land on the sentient planet Gaia, he and Dalton decided to stay behind and become the planet's caretakers.