In the mid—2250s, as a member of the science team involved in Project Purity, Catherine befriended and fell in love with the project's chief scientist, James. In late 2257, the two lovers conceived a child. Nine months later, on July 13, 2258, Catherine gave birth to a child. After seeing them, Catherine suffered from cardiac arrest and, despite attempts at saving her life by James, she died. Her death affected James deeply, who abandoned Project Purity soon after and traveled with his child to raise them in Vault 101.
Catherine dies in the prologue of the game. She appears during a cutscene that showed the Lone Wanderer's birth, but the only visible thing is her legs and her voice. A holotape recording of James flirting with her called "Better Days" can be located in the Jefferson Memorial's lower levels.
The storyline of Fallout 3 does not specify her ethnicity or her last name (the NPC used for her was not intended to be seen during normal gameplay).
In Point Lookout, while intoxicated on the Mother Punga, the Lone Wanderer will find one of the many giant bobbleheads on a medical examination table with a skeleton marked "Mom", balloons, and a party hat. The bobblehead will say "Blech. If my kid looked like that, I’d abandon it too." The skeleton is Catherine, reflecting the lack of maternal presence in the Lone Wanderer's life. Furthermore, the last bobblehead in the vision says, "Dead mother, life in a post-nuclear Wasteland and not a friend in it. Yeah, you aren't exactly blessed."
She is seen on a photograph next to James in Fallout: New Vegas in Vault 21 in Sarah's bedroom, although their likeness simply seemed to be recycled for that photograph like other Fallout 3 assets were.