All the monsters you ever had nightmares about are alive and sick and living at Blood Manor, a few miles from the Beltway in Waldorf, Md. There's Dracula, Darth Vader, Frankenstein's monster, even Son of Sam - everyone you need to get you in to the spirit of Halloween. It's open 7 to midnight Friday and Saturday, to 10 Sunday and Monday. For $2.50 you're guaranteed to be scared out of your wits, and the St. Mary's Creative Arts Forum gets half the money.

The spirit who realy haunts Blood Manor - who designs the guillotines, creates the bloody skulls, soins the cobwebs and masterminds the whole horror show - is not a monster but a "monsterologist" named Edwin "Itsy" Atkins. A rotund, bearded theatrical producer who drives a '48 Packard hearse, Atkins, 30, is dead serious about "monsterology."

"I prefer to call it theater of horror," says Atkins, a theater major who specialized in makeup at East Tennessee State College. "Instead of changing the scenery you leave the scenery stationary and make the audience move through a series of connected vignettes. Fear is a basic drive. People love to be scared, and this hasn't really been capitalized on."

Atkins' dream is to open a "classical horror" theme park in an English castle. "There's no Halloween there, so monsters are popular all year round," he says with ghoulish glee.

Monsters are popular in Maryland, too. Last year about 20,000 people toured Blood Manor and hundreds had to be turned away each night. This year Atkins plans to scare even more people, by speeding up the flow through the house. "We've learned how to scare them in the direction we mean them to move," he says.

The fun begins when you're waiting in line outside the house. All of a sudden the Texas Chain Saw Murderer, wearing a bloodstained butcher's apron, comes charging out of the woods and hacks at the guy in front of you. Don't worry, the chain saw doesn't have a blade and in case of mishap Blood Manor is insured with Lloyds of London for $1 million. And the guy in front of you is a stooge, probably a member of the drama group at Waldorf's Thomas Stone High School. Other stooges may get strung up on trees or attacked by an ax murderess. These diversions, according to Atkins, help both to pass the waiting time and to psych you up for the horrors to come.

In the daytime, Blood Manor looks like what it is - a ramshackle frame house that's about to be torn down. But after dark, with strobe lights and eerie music and disembodied bleeding heads floating around, Blood Manor is a haunting experience. When Dracula bites the neck of his victim, the girl's face changes color right before your eyes. (It's done with lights and makeup.)

In the spider room, cobwebs spun out of rubber cement drape all over you and make your flesh crawl - even before you spot the Spider Monster. Darth Vader attacks you with a real laser sword. At press time, Atkins was undecided about whether to use one room for the shower scene from Hitchcock's "Psycho" or for a vignette of "Alive," where members of a South American soccer team eat one another.

On your way out, you get to peek in the garage just as Son of Sam is doing his thing to a couple in a Volkswagen convertible.

Just when you think you're out of the woods, you're in them. You have to walk - most people run, actually - about a quarter of a mile down a wooded path to get back to the parking lot. But you won't be alone - a gorilla may swing down at you; you may encounter a headless figure carrying a bloody sack; you may even meet up with a shallygaster, a birdlike monster indigenous to Maryland swamps.

Needless to say, Blood Manor is not recommended for impressionable children - or impressionable adults.

Directions: From Beltway Exit 36, go south on Maryland Route 5 (Branch Avenue) about 14 miles to Acton Lane. Ben Davis' Steak House will be a gallows with a hangingfigure pointing left, down Acton Lane. You can't miss it.

If you think a haunted house is something, how about a haunted community center? The one in Beltsville (3900 Sellman Rd.) is guaranteed to be haunted through Sunday (but not Monday, when the haunts apparently have other haunts to haunts). Hours are 5:30 to 9 Friday, Saturday 1 to 9 and Sunday noon to nine. Admission is 75 cents (50 cents for senior citizens and children under 14), and group rates are available. 937-6613