Shortly before stardate 48315, that year, the Val Jean and the USS Voyager were both transported to, then stranded in the Delta Quadrant by the Caretaker's array. The Val Jean was destroyed by ramming a Kazon Predator-class warship while fighting the Kazon-Ogla, and as a result the crew of the Val Jean, Henley included, joined the crew of the Voyager as provisional officer's in Starfleet during Voyager's historic trek home. (VOY: "Caretaker")
Being unfamiliar with Starfleet protocols, she had a hard time adjusting to life on Voyager. She and three other former Maquis, Kenneth Dalby, Chell, and Gerron, were selected by Commander Chakotay to participate in Lieutenant Tuvok's Starfleet Academy-style crash-course aimed at bringing former Maquis members unfamiliar with Starfleet up to date. On the first day of training Tuvok had her remove her "festive" headband, as it violated regulations.
During a simulated battle exercise, Dalby ordered her to fire at will and do as much damage as possible to Romulan Warbirds attacking them. As a result, she, along with all the others, "died". Later, during one of the exercises, she, along with Tuvok and the rest of the team, rescued Gerron who was almost killed by a plasma leak. (VOY: "Learning Curve")
Henley was played by Catherine MacNeal.
According to the video game Star Trek: Starship Creator, Mariah Henley was born on Nuraka III to parents Loren and Donald Henley. She has a sister named Catherine.