Karen Watson was a troubled teenage girl sent to St. Mary's Home For Unwed Mothers after getting pregnant in 1964. While there she ended up killing another girl, Hilary West.
A troubled girl, Karen had been expelled from her high school sometime before coming to St Mary's for hitting another girl in the head with a rock. Years later, Karen would say "that harlot had it coming". Karen tended to view her unborn baby as a nuisance and the only reason she was stuck at St. Mary's. Karen had already been there for some time when Hilary arrived and warned her about the home's notorious Dr. Finnegan, a drunk with a reputation for allowing girls to die on his table. She also scoffed at Hilary's belief that her boyfriend Huck Oberland would marry her.
Even at St. Mary's, Karen acted out to some extent. When two young boys pelted the girls with eggs, Karen threw back rocks at them, which caused the home's nuns, Sister Margaret and Sister Abigail, to take her to an isolation room as punishment.
Karen was angry at Hillary at first for not backing her, though the two later bonded. Karen, Hilary, and a few other girls from the home were at a music store together when Hilary caught Huck there with another girl named Mary-Lou McLaren. Karen overheard Hilary threaten to tell Huck's parents about the baby herself if he didn't.
Sometime later, Karen gave birth to her baby, a boy. Though she had resented him all through the pregnancy, Karen fell in love with him on sight and was heartbroken to have to give him up for adoption with only fifteen minutes to say goodbye. Hilary tried to reassure her that he was going to a wealthy lawyer's family and that he would be well taken care of, Karen only repeated again and again that she wanted him back in his bassinet.
Sometime after Hilary had given birth, Karen caught her take her baby girl out of her bassinet and flee the home. Karen followed her into the woods, where Hilary told her she'd learned that St. Mary's was selling babies, rather than giving them away. Karen, having had to give her own baby, insisted that Hilary had to do the same. Then, in a moment of delusion, she started demanding that Hillary put him and that Hilary couldn't take Karen's baby before finally picking up a rock and hitting Hilary over the head with it. She picked up Hilary's baby and headed back to the home, leaving the fatally injured Hilary to die in the woods.
Karen put Hilary's baby in her son's bassinet, wanting to keep her, but soon realized there was no replacing her baby, and Hilary's baby was soon put up for adoption as well.
Karen would spend the next four decades searching for her son's whereabouts. When adoption search groups were formed on the internet, Karen joined every one.
In 2007, Hilary's daughter, now a grown woman named Barbara Lakey, having just discovered she was adopted, asked Detective Lilly Rush to look into her mother's still-unsolved murder. After learning of Karen's reputation from Sister Margaret, Lilly and Detective Will Jeffries questioned Karen, now an older woman working as a waitress.
Karen told them she had no grudge against Hilary and quickly deflected suspicion by telling them about the incident between Hilary and Huck in the music store. She also lied and said she'd never tried to look for her son.
After learning how Hilary's baby had been found in the bassinet of Karen's baby the morning after Hilary's murder, however, Lilly questioned Karen again. She told Karen how her alcoholic mother Ellen Rush had once abandoned her in a mall to get drunk when Lilly was six.
Karen brushed off giving up her son at first, saying it was "not a big deal", but her resolve slowly cracked as Lilly showed her files from online search group showing her trying to find her son.
Lilly finally told her she'd found Karen's son and that he wanted to meet her, offering Karen this in return for her telling the truth about what happened to Hilary the night of her death.
Though she would be charged for Hilary's murder, Karen could take comfort in known her search for her son was finally over.