A ghoulish operating room was a staple of Blood Manor, a haunted house operated by Itsi Atkins in Southern Maryland in the 1970s. (Itsi Atkins)

Itsi Atkins always believed that if he built it, they would scream.

And they did, by the thousands, at Blood Manor, the pulse-pounding, scream-inducing haunted house Itsi unveiled in 1971. When it became world famous — when a British tabloid called it “the sickest show in America” — Itsi knew that it had all been worth it — all that blood, all those severed limbs, all those fake guts and fake snakes, all those monsters, murderers and ghouls . . .

And to think it started in the wilds of St. Mary’s County, Md.

With Halloween bearing down on us like an ax-wielding maniac, now’s a good time to remember Edwin “Itsi” Atkins, pioneer of fright.

“In all my research, I can’t find anybody who has a live-action haunted house before 1971,” Itsi told me when I rang him up in Georgia, where he lives now. Yes, people had “yard haunts” — elaborate decorations in their front yards — and Disneyland had its Haunted Mansion. But that was an amusement-park ride, which took safely seat-belted riders through a gently scary attraction.

An abandoned convent was the site of the first Blood Manor haunted house, designed by Itsi Atkins in St. Mary’s County, Md., in 1971. (Itsi Atkins)

What Itsi claims to have invented is the interactive experience of walking through a haunted house while being assaulted by scary actors amid frightful tableaux.

“It is theater in reverse,” he said. “In theater, you stay in the chairs and the scenery moves in front of you. In my theater, you move through the house and the scenery stays permanent.”

Itsi grew up in Wheaton, Md., and studied theater at St. Mary’s College and East Tennessee State. In 1971, he was a 24-year-old elementary school teacher in Southern Maryland. He’d also taken a job with St. Mary’s County’s recreation department. “I didn’t know anything about sports — just music, arts and culture,” Itsi explained. “I said, ‘Let me handle fundraising. Let’s do a haunted house.’ ”

When he stumbled upon an abandoned convent in Ridge, Md. — the stairs creaky, the floors dusty, the basement full of oily water — he knew he’d found his setting.

He recruited local college students to build and staff Blood Manor. The horrors included a man hanging from a tree and a blood-soaked operating room where surgeons amputated a victim’s legs. In another room was an open casket containing a putrefying woman dressed for her wedding. The casket would close with a bang, and suddenly standing behind you would be the dead bride herself.

“I always had to hire twin girls,” Itsi said.

It took trial and error to perfect Blood Manor’s pacing and adjust the flow of guests.

Horrors in and around the haunted house setting included a man hanging from a tree and a blood-soaked operating room where surgeons amputated a victim’s legs. (Itsi Atkins)

“There was a science to moving them,” Itsi said. “You’re moving a movable force through a solid structure. And then you’re scaring them, which makes them move in the opposite direction. You’d have to scare them from behind so you were propelling them out of the room to the next room.”

One breakthrough was a gas-powered chain saw, from which Itsi removed the chain.

“It was terrifying,” he said. “The oiler, we had [fake] blood in it, so when you hit the pump, it spitted out blood. You could rake that across somebody’s arm, and they would think it was going into bone. The chain saw always cleared them out.”

Itsi and his collaborators spent each year dreaming up new features. He would capitalize on the news, one year installing a “Son of Sam” fright — before the serial killer had been caught — and another year featuring the South American rugby players from “Alive” gnawing on their teammates’ bones.

Blood Manor bounced around Southern Maryland, seldom in the same house twice. Wherever it landed, it attracted huge crowds and intense criticism. Some town leaders thought it was sick and twisted — and not in a good way.

By 1980, Itsi was itching to move on. He entered the movie business, working as a location manager. One of his main Blood Manor collaborators, Skip Smith, went on to be a makeup artist with CNN in Washington.

Itsi had trademarked the name “Blood Manor,” so when he saw the name being used for a Manhattan attraction — the sort of place lampooned in the “Saturday Night Live” David S. Pumpkins sketch — he sued them. They credited him with the name and concept on their website.

After living in New York City, Itsi moved two years ago to Milledgeville, Ga., where his mother had roots. “I came to the wilds of Georgia to try to restore a lunatic asylum,” said Itsi, 69. He added: “I’m getting a lot of resistance.”

Despite all the gore, Itsi thinks there was something pure about Blood Manor. It crystallized storytelling down to its barest essence and pulled from visitors the most sincere of reactions.

When the final curtain falls at a traditional play, he said, you look to your left and then to your right before deciding whether to clap. You make a conscious decision.

“In haunted house theater, it just comes out of you,” Itsi said. “You can’t help it.”

And instead of applause, it’s a scream.

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/johnkelly.