A prominent "surgeon to the stars", Charles built the famous Murder House in 1922 for his wife, Nora Montgomery. Although quite successful in the beginning, it is apparent that he began to lose business. He is described as having developed a gruesome "Frankenstein Complex", wherein he stitched the assorted body parts of animals together. He also became addicted to the drug ether.
Charles' wife Nora became frustrated with her husband's inability to pay bills, and for being less focused in work, so she took matters into her own hands. Nora came up with the plan for Charles to organize illegal abortions for him to perform in the house's basement. Young women flock to the Montgomery house for the procedure.
In time, Nora's plan falls apart because one patient "couldn't keep her mouth shut" and told her boyfriend what happened. Pursuing revenge, the girl's boyfriend kidnapped the Montgomery's son, Thaddeus, and dismembered him. The remains were later brought to Charles by the police in an evidence box.
Charles, having fully lost his sanity, put his skills to the ultimate test: he attempted to sew his son back together. Nora catches him in the basement and becomes horrified by what he'd done to Thaddeus. Charles was successful in bringing their son back to life, claiming he used the heart of "one of their girls". Charles' creation was a grotesque, demonic creature (the Infantata) that attempted to suck Nora's blood when hungry. Distraught by what their son had become, Nora shot Charles in the head then turned the gun on herself.
Charles' ghost manifests primarily in the basement and is shown to have fully devolved into the Frankenstein Complex that plagued him in his last months. In 1947, it was he who sliced the body of Elizabeth Short in half and emptied her innards after the then owner of the House (Dr. David Curran, a dentist) accidentally killed her. Curran looked on in horror as Charles gave her the historic "Chelsea Smile". When asked why he was cutting her in such a manner, Charles claimed it was to give her a permanent smile since he was disappointed as "she looked so sad". Curran would later dispose of her body in a vacant lot.
His various jars filled with fetus and animal parts were shown to remain or reappear in the basement during the time that the house was abandoned, until at least 1978, when Troy and Bryan were murdered by the Infantata.
Charles was amongst the assorted ghosts to manifest in the basement in the presence of Violet Harmon, where he mistook her for one of his patients. The number of ghosts shocked her and finally ended her doubts over the House being haunted.
When Travis' ghost laments that he would never become famous as the Black Dalia and Hayden (the latter having been the one who murdered him), Charles suddenly appears to the three. He offers to give Travis the fame he desires, then mutilates his body in the same manner he did to Short's. Hayden then called Larry Harvey to dispose of the body in a place where it would be seen.
Charles delivers Vivien's twins with the help of Gladys and Maria. He gives the allegedly stillborn child of Ben to his wife. Vivien would bleed to death after the procedure, despite Charles' efforts to help her. He then vanished with the other ghosts, leaving Ben alone and in tears with Vivien. 
- To Dr. David Curran: "I've bisected her body, removed the intestine, and drained her blood."
- To Dr. David Curran: "A writer writes, a surgeon cuts. I think you will find these pieces more portable."
- To Dr. David Curran: "She seemed so sad. I've decided to give her a quote that will last forever."
- To Nora: "What have you done to that baby? Can't even tell if it's a girl or a boy!"
- To Nora: "You'll see. They will write articles about me one day in the Boston Medical Journal."
- To Nora: "Your baby. He's upstairs. Go see him, he's waiting."
- Charles Montgomery is the fifth character to make a crossover appearance in another season. The Countess books an appointment with Charles to have a secret abortion in the basement of his house.
- His nickname is "Casper", given by Hayden.
- The name "Charles Montgomery" was the alias of Charles "Tex" Watson, a member of the Manson Family who was involved in the murders of Sharon Tate and Rosemary and Leno LaBianca.
- Regarding his dismembering of Short, Charles shares similarities with one of the most infamous real-life suspects in the case, Doctor Walter Bayley. He was a prominent surgeon who was believed to have performed illegal abortions and suffered from a deterioration of his sanity.
- It is likely that the case of Thaddeus going missing and later turning up dismembered was inspired by the real life case of the Lindbergh baby, who was also kidnapped and later turned up heavily decomposed and dismembered. This seems even more probable given his lace gown, which is nearly identical to the Lindbergh baby's.
- The musical theme which plays in almost every Charles Montgomery scene is "The Beginning" composed by Wojciech Kilar for Bram Stoker's Dracula.
- It is likely that he is related to Madison Montgomery. Both have abilities to resurrect the dead (Charles resurrected a stitched-together Thaddeus, and Madison resurrected a stitched-together Kyle). Another more prominent feature is their last name, Montgomery, and both share roots in Los Angeles.
- It is possible that Charles used blood obtained during Elizabeth's abortion, coupled with his innate witchcraft genetics, to resurrect his son into the Infantata. This would not only explain why the Infantata is a reanimated being opposed to a ghost, but would also explain why it possesses an unquenchable thirst for blood.