In the woods near Churchville, New York, the body of a young girl named Carla Castillo is discovered. Having been brutally raped and strangled to death, many of the police investigating the case believe her to be the victim of a disorganized killer who struck out in a fit of rage. Detective Megan Paige (Eliza Dushku) of the Rochester Police Department, however, has a different idea. Owing to her ability to focus obsessively on all of the minute details of the cases she works, Paige has built up an impressive track record of convictions in the past. And now, it is those small details that tell her this attack was anything but random. The facts that the killer redressed the victim after killing her, that several witnesses saw the girl getting into an unidentified vehicle of her own volition, and the strange "coincidence" that the initials of the girls name (C.C.) are the same as that of the town her body was dumped in all lead the young detective to believe that the crime is the work of a serial killer.
Facing opposition from her colleagues and superiors, Megan spends nearly every waking moment trying to find the connections that will prove her theory and uncover the identity of the killer. She grows so obsessed with the case that her fiance, another Rochester detective named Kenneth Shine (Cary Elwes), begins to worry for her health. As the weeks go by with no new leads, Detective Paige begins to notice strange things... she can hear the young girl's voice whispering to her, and at times can even see her ghostly figure standing before her, pleading for help. When Megan's captain takes her off of the case the strain finally becomes too much to bear, and, while begging for the forgiveness of the decaying young girl standing above her, Megan slashes her wrists.
Two years later, Megan is just starting to get back on her feet after receiving extensive treatment for what her doctors diagnosed as adult-onset schizophrenia. No longer a detective, Megan is able to convince her former fiance, now himself a Captain, to get her a job as a file clerk with the Rochester PD. Committed to getting her life back on track, Paige does her best not to think about the still unsolved Castillo case. She is forced to relive it once again, however, when the body of another young girl is found in nearby Webster, NY. A young girl by the name of Wendy Walsh. Certain that this is the work of the same killer that struck two years ago, Paige convinces Ewes to allow her back on the case. The stress quickly begins to take its toll, and Detective Paige soon finds herself in a race against time... both to stop the psychopath she's hunting from taking another young girl's life, and to silence the ghosts that are haunting her once and for all.
The Alphabet Killer provides examples of the following:
- Alliterative Name: This is how the killer chooses his victims, as well as the area he dumps the bodies.
- And I Must Scream: Paige, after discovering the killer's identity, is forced into a mental institution and sedated. It is implied that she remains there for years, unable to do anything as more and more ghosts of dead girls crowd around her.
- Defective Detective: Detective Paige always knew that she was different from her colleagues in her uncanny obsessive tendencies. She did not know, however, that it would lead to a psychotic break.
- Downer Ending: Paige is involuntarily committed to a mental institution as the killer escapes, with her unable to stop him from killing more girls, though she vows she'll find a way.
- Driven to Suicide: Paige, unable to cope with hearing and seeing the dead girl, attempted suicide by cutting her wrists.
- Narrowed It Down to the Guy I Recognize: The director deliberately made use of this trope to make the audience question who the killer might be by casting male actors who have played killers in other films.
- Cary Elwes, who plays Megan's colleague/former lover, starred as the serial killer Casanova in Kiss the Girls.
- Michael Ironside, who plays Wagner Police Captain Nathan Norcross, has played villains in numerous roles throughout his long career, including his roles in Scanners and Total Recall (1990).
- Carl Lumbly, who plays Paige's therapist Dr. Ellis Parks, did voice work as the villain "Stalker" in Batman Beyond.
- Bill Moseley played Otis Driftwood in House of 1000 Corpses and The Devil's Rejects.
- Obfuscating Disability: Ledge, who fakes being wheelchair-bound to remove any suspicion that he might be the killer.
- Serial Killings, Specific Target: According to Ledge, Carla Castillo was supposed to be his one and only victim. When he met Detective Paige, he committed the second and third murders (again, according to him) so that the police would realize that her serial-killer theory was right and give her back her job.
- The Sponsor: Though it is not drug related, head of Paige's support group Richard Ledge acts in this capacity for her, giving her advice on dealing with the resurgence of her visions and even helping her out when she later gets in trouble with the police. He's the killer.
- Very Loosely Based on a True Story: The plot is based on the real-life events of the unsolved Alphabet murders that took place in New York in the 1970s. The screenwriter took great liberties with the details, however, and one of the few similarities left to the actual case was the killer's choice of victims with alliterative names.
- Working with the Ex: When Paige is allowed back into the force on desk duty after receiving treatment for the mental breakdown she had during the Alphabet Killer investigation years ago, she finds that her ex-boyfriend/ex-partner is now Chief of Police, and thus her boss. This puts him in an extremely awkward position when the killer resurfaces, as no one knew more about the case than Paige did.
- You're Not My Type: When the eponymous serial rapist/murderer (who happens to only target pre-teen girls with Alliterative Names) captures the female cop who has been hunting him, he laughingly says this while driving to the place where he plans to kill her and dump her body.
A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y and Z. Now, I know my ABC's...