In 2269, Ensign Mallard joined a four-man landing party to search the surface of Gobi III for the missing crew of the USS Pasteur. The landing party was knocked out by a disruptive transporter beam, and Mallard was the last to awaken in a decontamination unit.
When the android Avatar interviewed the landing party, Mallard slipped away to recover their weapons. Unfortunately, before he could reach them, a high energy scan recorded his DNA, and the scan killed him. (TOS - Year Four comic: "Issue 6")