When Ballard entered Starfleet Academy, she became close friends with Harry Kim, who lived across the hall in their student dorm. She taught him to ice skate, despite his dislike for cold weather. During her Academy years, she never knew that Kim had a crush on her, and that being in the same classes as him was not a coincidence. Her favorite things to eat were peanut butter and jelly sandwiches; during dinner with Captain Kathryn Janeway she mentioned that she used to live on them during her Academy years. Her sloppiness sometimes caused Kim to ask for a baryon sweep of his room.
Ballard's favorite saying came from an old Klingon battle cry, "Own the day." She believed in attacking each day and possessing it. According to Kim, that was what made her so much fun to be around.
In 2371, Ballard graduated from Starfleet Academy as an ensign and was posted to the newly-commissioned USS Voyager under the command of Captain Janeway. There, she was reunited with Harry Kim. Her primary post was in main engineering.
In 2374, Kim and Ballard were assigned to an away mission on a class M planet in the Vyntadi Expanse to investigate readings of dilithium ore. However, it was a trap by a Hirogen hunting party, who had reconfigured a power cell to give a false dilithium signal. During their retreat to the shuttle, Ballard was hit by a neural disruptor and died on the way back to Voyager. Harry Kim gave the eulogy, and she was buried in space. Her personal effects were placed in storage. (VOY: "Ashes to Ashes")
In 2376, she returned to Voyager and attempted to resume her life as Ballard. However, she discovered after a short time that her mind and body were no longer Human, and The Doctor's best efforts to restore her Human appearance were only cosmetic and temporary, eventually reaching a point where she would have had to spend most of the day in sickbay just to look Human. During her time away, she made a list of the things she wanted to do if she ever returned to Voyager. Eating Jiballian berry salad was #6, dazzling B'Elanna Torres was #16, hearing Harry play his music was #26, showing up for duty shifts on time was #27, and making Tuvok laugh was #32.
She eventually returned to the Kobali when Voyager was being attacked by them, demanding she return. She came to realize that she didn't belong on Voyager anymore, and made the decision herself to go back. According to her, Lyndsay Ballard died three years ago and she could no longer deny this. (VOY: "Ashes to Ashes")
Lyndsay Ballard was played by Kim Rhodes.
Ensign Ballard's original "death" was not shown on screen or mentioned in an episode around the time it happened, only in this episode. Ballard mentions a date of death as stardate 51563, which would have placed it between the episodes "Hunters" and "Prey", from 2374 in Season 4. When unpacking with Kim, though, she mentions being gone for three years – leaving a year of death in 2373. Also, she did not remember Tuvok being promoted to lieutenant commander, which happened in early 2374, on stardate 51186.2, long before "Hunters". The story she originally tells Captain Janeway, including six months of travel in a shuttlecraft, adds up to approximately 2.5 years – all of these are before the crew met the Hirogen for the first time.