Ensign Lang was an operations division Starfleet officer assigned security aboard the USS Voyager, under Captain Kathryn Janeway. She was one of several crewmembers that survived the transport to the Delta Quadrant in 2371.
Later that year, Lang was temporarily promoted to chief of security after a majority of the Voyager crew had been translocated to the Nyrian biosphere vessel. She later was in command of the starship after Chakotay left the bridge. While in command, she coordinated with two of the remaining twelve crewmembers that they had to prevent the Nyrians from capturing the bridge. Seconds later, several Nyrians stormed the bridge and Lang stunned two of them, before she was, herself, stunned. She was subsequently transported to the biosphere ship, where she was imprisoned with the rest of the crew. (VOY: "Displaced")
In 2377, she was affected by radiation when a mine exploded near Voyager's hull. She and the rest of the crew (except The Doctor) left in escape pods and were rescued by the Quarrens, and treated for their radiation burns. However, what the crew didn't know was that the Quarrens intended to alter their memories, and make them join their working class.