|“||I'm sorry! I'm sorry! I did things, I d- I did them. Uh...you Tara? Yeah, I did things 'cause he, uh, told me to, so...that's why I did it.||”|
Desmond, a native of Franklin, Tennessee, developed dissociative identity disorder (DID) after his mother died and his abusive stepfather often subjected him to games of Russian Roulette. As a result, he sought treatment for his disorder. His therapist once attempted to use hypnosis to help him recognize his alternate identities, but the procedure caused him to have a seizure and then lapse into a catatonic state, which he didn't recover from for six months. Prior to Mirror Image, he was hired by Peter Lewis to deliver some equipment to him. Unbeknownst to Desmond, Peter was a serial killer by proxy who escaped from prison and tracked Desmond down using a stolen list of DID patients countrywide. Peter proceeded to drug Desmond and brainwash him into believing he was Gabriel Lewis, the brother of Doctor Tara Lewis, with the real Gabriel being held captive by Peter.
Acting under Peter's suggestion, Desmond meets Lewis at the coffee shop, tells Lewis about her being in the FBI, and calls her by her nickname of "T". Lewis becomes shocked by the amount of information Desmond knows and gets him to give her his phone under the threat of arrest. After she verifies that he has Gabriel's phone, Lewis asks Desmond who he is, and he replies that he is Gabriel. He is then taken to the BAU interrogation room. JJ enters and asks him a series of questions pertaining to Gabriel's personal life; Desmond answers all of them flawlessly and even gives a heartfelt, legitimate response as to why he calls Lewis "T". Later, Lewis enters the interrogation room, shows Desmond photographs of the real Gabriel (which she and Alvez found in a room rented out by Peter under an alias), and asks about one of them (which depicts Gabriel at the age of fifteen) as she doesn't remember it. Desmond refuses to cooperate anymore, leaves the room, and is about to walk into the elevator when Alvez approaches him and introduces himself as Lewis' coworker.
Then, Lewis arrives and recounts the incident where Gabriel had been beaten up by the bullies. Pretending that Desmond is Gabriel in an attempt to move the investigation forward, Lewis then apologizes for her recent actions and says that she wants him to stay. Satisfied, Desmond says that if she wants to learn about the photo, she has to bring Albert to him. Lewis is forced to accept the condition and convinces Albert to play along. The two enter the interrogation room and ask him about the photo. Desmond proceeds to recount the story of Gabriel's trauma over having to stop Albert from committing suicide with a shotgun. This causes Albert to leave in tears. Later, Lewis tells Desmond about his traumatic childhood and mentions his real name while apologizing. This brings Desmond out of his hallucination and he starts slipping into catatonia, but Lewis manages to coax him out of it. He starts to cry and apologizes for doing the things that he did. He then tells Lewis that he saw Gabriel and that he is still alive. Desmond also tells Lewis about the warehouse where Peter is holding Gabriel, and how he was forced to retrieve something from Albert's house for Peter. This causes Lewis to realize that Desmond retrieved her father's shotgun and that Peter plans to kill Gabriel with it. Desmond wasn't seen afterwards, but was most likely returned to Franklin, Tennessee, and institutionalized.
- Desmond is partially similar to Brian Phillips as both suffered from dissociative identity disorder and were forced by Peter Lewis to assume identities that were not their own or their normal alternate personalities.