Ralston was a 23rd century Human man who served Starfleet as a security officer, assigned to Federation starship USS Enterprise in the 2270s. 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.