In 2362, while still an ensign serving aboard the Victory, Brevelle was a member of an away team on Tarchannen III, along with Lieutenant Susanna Leijten, Ensign Geordi La Forge, Ensign Emilita Mendez, and Ensign Paul Hickman. They were investigating the mysterious vanishing of the staff of an outpost. During the mission, the entire away team was unknowingly infected with alien DNA.
In 2367, Brevelle was working at Starbase 112 when the alien DNA finally affected him. He deserted his post, stealing a shuttlecraft. It had forced him and Mendez, and eventually the rest of the away team, to return to the planet Tarchannen III. Both Brevelle and Mendez fully transformed into alien creatures, and because their conditions couldn't be reversed, they were left on the planet to live out their days. (TNG: "Identity Crisis")