It’s fairly easy to plot a contemporary horror novel if you know the formula, which is also fairly simple--quite simple, in fact, consisting of three phases:
- A series of bizarre incidents occurs.
- The main character discovers the cause of the bizarre incidents.
- Using his or her newfound knowledge as to the cause of the bizarre incidents, the main character (usually assisted by others) puts an end to them (often by killing a monster).
- Establish the cause of the series of bizarre incidents; if the cause is human or humanoid (for example, a monster with a will and personality), give it a plausible motive for its actions.
- Make a list of the bizarre incidents that will occur.
- Establish the means by which the main character learns the cause of the bizarre incidents.
- Have the main character use this knowledge as to the cause of the bizarre incidents to put an end to them.
- It helps (but is not mandatory) to associate the monster or other cause of the bizarre incidents with a real-life horror.
In a nutshell, that’s all there is to plotting the contemporary horror novel.
Let’s conclude with an example (Stephen King's Desperation):
- Establish the cause of the series of bizarre incidents. The demon Tak escapes from the caved-in mine in which he has been imprisoned for several decades and battles God, seeking to demonstrate its superiority to the Christian deity.
- Make a list of the bizarre incidents that will occur. In Nevada, a dead cat is seen nailed to a highway sign. An abandoned recreation vehicle (RV) sits alongside a lonely stretch of highway, its door flapping in the breeze. A sheriff, acting crazy, arrests a couple on trumped up drug charges, threatening to kill them on their way to jail. The nearest town, Desperation, seems abandoned, except for the corpses that litter the streets. The sheriff has arrested several other individuals, also on false charges; among his prisoners are the members of the RV family, whom he supposedly rescued from (non-existent) gunmen. Vultures, scorpions, wolves, and other animals, under the sheriff’s telepathic control, attack people. A preteen prisoner, David Carver, miraculously escapes from jail, afterward performing additional miracles (using a cell phone with a dead battery and multiplying a supply of sardines and crackers). The demon Tak, who is behind the series of bizarre incidents, serially possessing the sheriff and others as he wears out their bodies, fears the preteen. Strange idols cause sexually perverse thoughts and feelings in those who touch them.
- Establish the means by which the main character learns the cause of the bizarre incidents. A character who has witnessed several of the bizarre incidents that befall his town tells David and the others in their party about the demon that has escaped from the caved-in mine and how it possesses one person after another.
- Have the main character use this knowledge as to the cause of the bizarre incidents to put an end to them. Assisted by others, David reburies Tak inside the collapsed mine.
- It helps (but is not mandatory) to associate the monster or other cause of the bizarre incidents with a real-life horror; for example, the monster of cause may symbolize such a real-life horror. Tak could represent social anarchy and its consequences.
Presto! Flesh out the skeleton of your story, possibly adding a related subplot or two, and you have the plot for one scary horror novel (especially if you happen to be Stephen King.)