It was a dark and stormy night ... at least a trial run for one.

Hundred Acres Manor, in South Park, opened its doors last week to a curious conclave of haunted house professionals on tour as part of the International Association of Haunted Attractions convention in Columbus, Ohio.

Those on the tour were given a sneak peek of the popular South Hills attraction's plans for the coming Halloween season.

"It was the best I've seen yet," Ronnie Browning, of Kokomo, Ind., said of the haunted house. "I loved the detail, the length and the maze."

He was amazed at a scene in which the "ghost" of the Lord of the Manor appeared above a casket and taunted visitors, who then went on to navigate a maze of "lost souls."

Mr. Browning and Ronnie Catron, co-owners of Twisted Darkness in Kokomo, were among the 147 producers, actors, makeup artists and set builders on a tour of top-rated haunts throughout the Tri-State.

The three-bus tour originated at the group's 2009 Midwest convention in Columbus. Its other stops included Kennywood amusement park's Ghostwood Estate, a dark ride through an eight-room haunted mansion that opened last year. They also saw Demon House in Monongahela.

"You really can't scare us. We come to look at the cool things," said Kathy Schieferstein, a haunted house actor.

She said re-creations of severed heads, screaming vixens and ghosts in a family cemetery are her equivalent of "a day at the beach."

In its sixth year, the nonprofit Hundred Acres Manor benefits the Homeless Children's Education Fund and Animal Friends. Last year, more than $45,000 was donated to each fund through the paid admission of 24,500 visitors.

The house, which has a castle-like facade, was once the bathhouse of One Hundred Acre Pool, known generally as Sully's Pool, which operated from 1938 to 1977.

In 1992, following extensive volunteer work, the site became home to Phantoms in the Park, followed by Hundred Acres Manor.

Ted Sobek, 55, of South Park, president of Haunted Acres Manor, said last week's tour prompted the organization's 170 volunteers to prepare the haunt early.

"We're 80 percent ready for this year," he said. "Now we can really concentrate on details to make better definition of scenes."

In addition to a redesigned layout to reflect the annual change in the story line, new chills will emanate from a gargoyle display in which an actor situated on its wings like a prop suddenly springs to life to unhinge the faint of heart.

Among the cast of haunters last week was Charley Thornton, 14, of Mt. Lebanon, who hid in plants on a bridge in camouflage.

"It's really fun to jump out and scare people," said the Jefferson Middle School student.

Also on hand was Tom Strong, 40, a Mt. Lebanon High School physics teacher who volunteers year-round as locksmith, electrician, carpenter and more.

"Most of it I learned here," said the Bethel Park resident, who, unlike Charley, prefers to stay in the shadows.

"If the patron sees me, something's wrong," he said.

Hundred Acres Manor, off Corrigan Drive in South Park, will be open from Sept. 25 through Oct. 31. For more, visit www.hundredacresmanor.com.