Noir is horror's hardboiled cousin. Noir, meaning black in French, is a subgenre of mystery that explores gritty, urban landscapes with a cynical detective who uncovers dastardly deeds. The darkness of noir is what lends it so perfectly to the horror genre. Both face dark truths that lie under the guise of normalcy. Both deal with outsiders who see the world as it truly is, be that outsider a hardboiled gumshoe or Frankenstein's monster. When Frankenstein's monster becomes the sardonic investigator, noir horror is born. Of course, that's a pretty simplistic view of the genre.
Noir, as a subgenre, did come from the hardboiled detective novels of the 1940's, but an important distinction between the two is that the protagonist does not need to be a detective or investigator. The protagonist can, in fact, be anyone so long as their attitudes match the gritty setting. Noir horror protagonists are notably outsiders who see the ugly truth of the world they live in. The are generally cynical in nature, and have the potential to be destructive either to themselves or others. Frankenstein's monster, without being a hardboiled gumshoe, is a great example of a horror noir protagonist in that he sees the world as evil and heartless and eventually changes to fit this mold.
The world, or setting, of horror noir could almost be considered a character itself. Squalid, debauched, typically urban settings are common, brimming with forces that are hostile toward the protagonist. This can be anything from a dark, careless city, like Gotham in the Batman comics, brimming with violence and mayhem to supernatural and otherworldly forces that have no use for humanity. Most importantly, the setting should be just as depraved as the characters and the events that unfold around them.
Another important aspect of noir horror is the tone. As its name suggests, this subgenre is relentlessly dark. The tone of works of horror noir is one of despair and suspicion. Themes often center around greed, corruption, oppression, or revenge, and while happy endings in horror are rare, they are particularly hard to come by in the noir genre.
Level of Characterization: Characters in horror noir will share a cynical worldview and bleak outlook, but beyond that characterization is varied. Some follow the traditional hardboiled model and cast the protagonist as an investigator, but others cast monsters or sorcerers as the main character. So, look for moderate to high levels of characterization.
Level of Plot: The level of plot in noir horror is variable, but generally high. One of the hallmarks of a well written horror noir is complex layers. Most will also contain a mystery of some sort.
Level of Supernatural: Varies, noir horror can feature the fantastical, but not always. A sample of the subgenre is as likely to contain human thrills and chills as it is to have supernatural.
Level of Scary: Noir horror contains a moderate to high level amount of scare, similar to that of psychological horror. A good portion of this comes from the tone and mood of the piece.
Level of Violence: Moderate to high, the level of violence in horror noir is dependent upon the mood of the piece, but it is generally higher than what you would find in atmospheric horror, gothic horror, or horror comedy.
Typical Setting: The typical setting of horror noir is a gritty, urban landscape that is rife with oppression and corruption. This can vary slightly, but there will always be a level of coarseness in the setting itself that will reflect the tone of the piece.
Southern gothic, Lovecraftian, Supernatural, Psychological, Crime, Serial Killer, Cult, Satanic, Atmospheric, and splatterpunk are all related subgenres to horror noir. Some of these, such as crime, supernatural, and Lovecraftian, are related due to the fact that horror noir borrows characters, settings, and tropes from these subgenres.
Others, like Southern gothic and splatterpunk produce the similar feeling of decay and despair that is typical of the horror noir subgenre.
Grit and cynicism. The overarching theme of the horror noir genre is one of world-weariness and the idea that dark secrets lurk beneath a surface of normalcy. If you like your horror straight-up with no hidden meanings, horror noir is probably not for you. If you are more into light-hearted horror, this subgenre is not for you. That being said, there are some horror noir stories that have comical aspects. However, overall, this genre is one of the darker of the horror genres. If you don't like the bizarre and outlandish, horror noir may also not be for you.
Call of Cthulhu by H.P. Lovecraft- Lovecraftian horror is a genre unto itself with its tales of monsters and madness, but the tale of one man narrowly escaping insanity in a small town that harbors a secret cult that worships a heartless monster, definitely falls within the definition of this subgenre also.
Falling Angel by William Hjortsberg- In 1950's New York, a private investigator takes on what he thinks is a routine missing persons case, only to find himself embroiled in a disturbing world of black magic. Adapted into the 1978 movie, Angel Heart, this story is considered to be one of the first of the horror noir genre.
Koko by Peter Straub- Four Vietnam veterans are the only people who can track down a mysterious and brutal killer. The first in the Blue Rose trilogy Koko is a taut, psychological thriller where hidden secrets struggle to remain buried.
Books of Blood by Clive Barker- Books of Blood are the collection of short horror stories that launched Clive Barker's career in 1984. The stories range from bone-chilling to gruesome to humorous. Themes of alienation and corruption are among those that you will find in these stories.
Headstone City by Tom Piccirilli- Nominated for the 2006 Stoker Award, Headstone City is the story of Johnny Danetello, a cab driver who can talk to ghosts and his unfinished business with the mob family that has a price on his head.
Greywalker by Kat Richardson- When private investigator, Blaine Harper dies for two minutes, she awakens to a new role as a Greywalker, someone who can travel between the human world and what lies beyond. The first in the series, Greywalker combines a supernatural thriller with a hardboiled detective story.
Procession of the Dead by Darren Shan- The first in The City trilogy is a dystopian thriler. Capac Raimi moves to the City and winds up working for the enigmatic Cardinal who knows all the inner workings of the gritty and corrupt City.
A Madness of Angels by Kate Griffin- Matthew Swift is awakened two years after his death, confused and sharing his body with spirits called electric blue angels. As he searches for answers, he is drawn into a plot to destroy his murderer and save the city.
Desperation by Stephen King- Travelers go missing when they drive down Highway 50 in Nevada, kidnapped by the deputy of a small mining town called Desperation. When the officer's victims attempt to free themselves, they discover hidden secrets about their captor and the town where they are held.
Big Machine by Victor LaValle- Ex-junkie and survivor of a suicide cult, Ricky Rice is inducted into a society of paranormal investigators, the Unlikely Scholars, who are all misfits in their own way. As Ricky adapts to life with the group, he is summoned by the shadowy Dean to thwart a rogue Scholar. LaValle's writing has been compared to Edgar Allen Poe and has all the creepy trappings of noir horror: the supernatural, a cynical protagonist, and an enigmatic authority figure.