Sophia is also the wife of Miles Balfour, and the mother of their only son, Ryan, who had been forming a friendship with small time drug dealer Dustin McEvers. Upon meeting Dustin, Sophia was originally unaware of his drug dealing activities, but began harboring hatred towards him after learning the truth: that he was not only a drug dealer, but that Ryan was his main customer. Sophia's visits to Dustin led Miles to believe that they were having an affair, but in actuality, she was seeing him because it was the only way she could see Ryan. Seeing Ryan immensely high on drugs drove Sophia into a rage, as she blamed Dustin for Ryan's habits (despite them being on Ryan's own free will).
Sophia then planned to kill Dustin, as she had frequented a shooting range and practiced on firing a shotgun. Later on, Sophia again met with Dustin and offered to pay him to cut ties with Ryan--something she had done in the past. The offer was $25,000, and Dustin agreed to meet Sophia at her home under the belief that he'd be paid. However, the evil Sophia unleashed her shotgun and pointed it at Dustin, stating that "this has to end" before shooting him to death. The villainess killed Dustin before he got the chance to defend himself with his own gun, and after Miles arrived, he covered for his wife and even took the fall, stating that he killed Dustin in self-defense.
However, Angie Flynn's investigation eventually revealed the couple's plan, and the episode's climax saw the Balfours at the station, with Angie revealing that Miles wasn't the killer and that he was covering for Sophia. Even so, the couple claimed self-defense, but Angie stated that wasn't true either, as the bruises on her shoulder proved that it was premeditated. Sophia later confessed, stating that she had arranged a payment to Dustin in exchange for steering clear of Ryan, and lured him to her home so she could kill him. She stated that it was either Dustin's life or Ryan's regarding her decision, and afterwards, Sophia was handcuffed and arrested for the murder.
- Jennifer Beals also appeared on Castle as the evil Sophia Turner.