|“||I would never do anything to hurt you. No. I created you.||”|
— Maggie to Lila
Not much detail is disclosed about Maggie's past, other than she was friends with Lila Archer, who attended the same college as her, and shared her room with her for one weekend after the heat to Lila's apartment was cut out. What happened during that weekend is only hinted at by Lila (who may have been merely caught up in her delusions and therefore may have provided false information), but ultimately left unsaid. As a result, she developed a homosexual and extremely morbid fascination with Lila. When Lila became an actress, Maggie became Lila's production assistant. She then began stalking her and killing anyone who wronged Lila in some particular way or threatened her career. First, Maggie killed Wally Melman, a producer who turned Lila down for a role in favor of an actress named Natalie Ryan, and then murdered Chloe Harris, another actress whom she saw as a potential rival for Lila, over a month afterward.
At the beginning of the episode, Maggie, disguised as a script courier, delivers a manila envelope to Natalie Ryan. As Natalie answers the door to retrieve her script, Maggie shoots her at point-blank range in the forehead. Natalie's fiancé, a producer named Jeremy Collins, walks in to see her dead, and Maggie kills him as well. At the scene of the murders, Gideon and Reid meet Detective Owen Kim, who tells them that two other murders have occurred similar to that of the present crime scene. The victims were also an actress and her producer; Gideon agrees to help with the case. During the investigation, Gideon is told that another actress, revealed to be Lila, had not only received threats, but strange gifts as well. The team realizes that they may be dealing with a stalker. Lila tells them she receives Red Anemones (her favorite flower) on the 7th of every month. The first suspect is Michael, Lila's manager; however, upon entering his office, he is found dead. Also found is an envelope with sensitive pictures of Lila, which were taken by a paparazzi named Joseph Martinez, which shifts the investigation onto him. While at Martinez's apartment, the team finds close-up photos of Reid. Theorizing that he may be the next victim, they leave the apartment to ask Lila more questions. Suddenly, a motorcycle passes and a bullet strikes Detective Kim; he is only slightly wounded, but is taken to the hospital.
Reid later notices a strange artwork on Lila's wall and realizes it is actually a cut-up collage of Lila's life; she explains that her producer had given it to her. The team interrogates him under the belief he is the stalker, only for him to reveal he originally received the work from Maggie, Lila's production assistant, causing them to realize that Maggie is the killer. The realization is confirmed when Lila's phone rings and it is Maggie. According to Garcia, the call is coming from inside the house. As Reid turns back to Lila after his conversation with Garcia, they hear Maggie slam down the phone in another room. Reid asks Lila how she could have gotten in, and Lila explains Maggie has keys to her place. Reid draws his gun to look for her, since he knows that she will be armed. As they go from one room to another, Maggie steps from around a corner and puts her gun to Lila's head, trying to get Lila to go with her.
When Reid tells her not to shoot Lila, Maggie replies that she would never hurt Lila because she loves her, to which Reid responds Lila doesn't love her back because she loves him before telling Lila to tell Maggie about how they kissed in the pool. Hearing it from Lila causes Maggie to snap; she pushes Lila away and turns the gun on Reid, who then disarms her. She tells him to shoot her, but he tells her that they can get her help. It is very likely that she is institutionalized afterwards due to her current mental condition.
The unsub was originally believed to be a single man, aged in his late twenties to early forties, who would be a meticulous and intelligent loner who can easily blend in regardless of the location, and knows how to cover his tracks. Unlike most serial crimes, the unsub shows absolutely no sexual component or signature, while the type of victim and weapon uses, a small and efficient .22-caliber handgun, indicates that he is an assassin, specifically a type 4. Type 4 assassins usually suffer from some sort of mental disorder, and are frequently delusional. Usually, this type of offender concludes in either suicide, or them killing the object of their affection if they feel rejected.
When the unsub's connection to Lila is discovered, he is profiled as having erotomania, meaning sufferers of that condition believe someone, usually of a higher social class, is in love with them. Originally just a stalker, the unsub evolved to killing people, and became something of a violent guardian angel to Lila, eliminating her competition in an attempt to further her career. When the authorities became involved in the case, the unsub's agenda altered, and his focus shifted from those around Lila to her directly, which is not atypical behavior for stalkers. Anyone with even the vaguest association to Lila would be in danger if the unsub mistakes them as competition for her affection. The unsub probably has a job that offered them a lot of free time that he uses to spy on Lila and prospective victims. Communicating with Lila through letters means he has started to feel like she owes them, and the tense used in letters implicated he knows her personally.
Maggie targeted people who had wronged Lila in some way or posed as a (perceived) threat to her career. She usually killed her victims by shooting them execution-style with a .22-caliber Harrington & Richardson Model 929 revolver, the shots being directed to the forehead. The only exception to this was Jeremy Collins, who was shot three times in the chest out of necessity, since he stumbled upon his girlfriend Natalie Ryan's murder and had no connection to Lila whatsoever. Her victims were often attacked at some point during their weekly routines; Wally Melman was killed outside a massage parlor he frequented, while Chloe Harris was killed while walking her dog along its usual route.
- Unspecified date-March 2006: Lila Archer (stalked only)
- January 10: Wally Melman (a producer who had turned down Lila for a part)
- February 28: Chloe Harris (an actress and potential rival of Lila)
- March 27: The shooting at Natalie Ryan's house:
- Natalie Ryan (an actress picked by Wally Melman instead of Lila; killed along with Jeremy Collins)
- Jeremy Collins (a producer and Natalie Ryan's fiancé; incidental; shot three times in the chest)
- March 28: Michael Ryer (Lila's manager)
- March 28-29:
- The drive-by shooting:
- The standoff at Lila Archer's house:
- Lila Archer (held at gunpoint and intended to kill)
- Spencer Reid (attempted; tried to shoot, but was subdued by him)