Lieutenant Ralston was a member of a security detail that accompanied a landing party to Zeta Reticuli II, a planet with a civilization similar to that of ancient Egypt. When a statue of a sphinx began to move and attacked the landing party, Lieutenant Pavel Chekov ordered the security team to scatter and take cover, but Ralston said he could handle the creature. The sphinx immediately killed Ralston with beams of phased light from its eyes.
Because it was standard operating procedure to retrieve Starfleet-issue equipment from casualties, Dr. Leonard McCoy took Ralston's communicator. Commander Spock was later able to contact McCoy on Ralston's frequency after the mentally-controlled Captain Kirk destroyed the communicators of the other landing party members. (TOS comic: "We Are Dying, Egypt, Dying!")