First appearing in Season 11, Episode 11, "Entropy," Cat Adams is introduced as a member of a mysterious assassin-for-hire group operating in the dark recesses of the internet. In time, viewers learn that when Adams was a child, she suffered abuse at the hands of her father, Daniel. After her father was imprisoned for the death of her mother, Adams was placed into the foster system, where she again was abused, this time by her foster father, who she eventually killed.
When her biological father was released from prison, Adams searched the world for him, intent on delivering her own sense of justice for his crimes. As her hunt continued to prove unfruitful, Adams began targeting other men she felt deserved punishment. Eventually, she became a contract killer, who, unlike her "colleagues," preferred to kill her targets face to face. Her work and modus operandi, which earned her the nickname "Miss .45," brought her to the attention of the FBI.
In "Entropy," the BAU set a trap for Adams, with Spencer Reid (Matthew Gray Gubler) posing as a potential new client for the assassin. After an intricate game of cat-and-mouse, Reid tricked Adams into believing he had found her father and arranged for her to meet him. The ruse worked, and Adams was arrested. Unfortunately for Reid, Adams' obsession with punishing men narrowed to one man in particular: him.
