Mary Corbis (Kirsten Potter) is the main villainess from "Mother and Child in the Bay," episode 2.02 of Bones (airdate September 6, 2006). She is a veterinarian and the mother of Robbie Corbis, and a friend of Carlie Richardson.
Carlie was found deceased in the episode's opening, as was her unborn baby, and regarding Mary, she was one in a group of mothers interviewed by Dr. Temperance Brennan and Seeley Booth, with the group revealing that Carlie was unhappy in her marriage to Kyle Richardson, who Mary revealed was abusive and added that Carlie didn't want her baby. Kyle ended up suspected due to this, as was his illicit girlfriend, Karen Tyler, but the Jeffersonian's investigation revealed a twist: the remains of the baby found with Carlie's body was an actually born baby, not a fetus. The baby's cause of death being shaken baby syndrome ended up revealing that the murderess was none other than Mary, as the baby found was the real Robbie Corbis.
As it turned out. Mary suffered from post-partum depression following Robbie's birth, and while Robbie was crying, Mary shook her son in an attempt quiet him, only to end up killing him instead. Driven insane due to losing her son, the evil Mary pursued Carlie and stabbed her to death, after which she took Carlie's baby from the womb and raised him as her own, even naming him Robbie. Brennan and Booth (along with a social worker) confronted Mary at the park, as they were set to take "Robbie" from her and informed her that he was Carlie's baby. The villainess insisted that Robbie was her son and regarding Carlie, she stated that Carlie wished that she never became pregnant and that it was wrong for her to have her child, and adding that the real Robbie's death was a mistake. Afterwards, Mary was arrested for the murders and for kidnapping Carlie's baby.