Prescott was a terran marine assigned to a world threatened by the Zerg Swarm along with Charn, Kort and Garrick. He was a jumpy new recruit on his first assignment, who Kort and Garrick would regularly intentionally scare.
He and the other marine's orders were to wait until the main zerg swarm were spotted, then let the ghost in command call down a nuclear strike. He would then call for an evacuation ship. When the ghost stopped responding to their communications they agreed one of them would go out of their bunker to meet him.
They played a card game to decide who, but Prescott got the lowest hand when he attempted to get an inside straight in a deck that was missing a queen. However, Charn realized Garrick was cheating and called him out. Garrick went berserk, and shouted at Prescott that he had served enough time, and that no matter how the card game went he would be the one to go. Charn eventually volunteered to go.
McAleese, Danny. "The Exit." (July 1, 2014). Blizzard Entertainment. StarCraft Lore: The Exit Accessed 2014-07-02