When Andy Thomas and Kate Willoughby ventured inside South Park's Hundred Acres Manor on a dark and almost-stormy night earlier this month they were ready for the usual Halloween sights: ghosts, vampires, goblins and lots of gore.

What they did not expect was to be really scared.

"We came for a thrill and left with a heart condition," joked Ms. Willoughby.

"She was hanging on so tight, she almost yanked my arm out of its socket," Mr. Thomas said.

In its fifth year, the Halloween frightfest at the nonprofit, all-volunteer Hundred Acres Manor, One Hundred Acre Drive, is open Wednesdays through Sundays, now though Nov. 1. Castle gates open at 7:30 p.m. They close at 10 p.m. Wednesdays, Thursdays and Sundays and at 11:30 p.m. Fridays and Saturdays.

Best of all, said the couple -- Ms. Willoughby is 24 and from Dormont; he is 27 and from Green Tree -- the spooky fun is for a good cause.

Proceeds benefit 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 23,000 visitors. The rest of the funds helped defray expenses, such as $22,000 to the county for rent.

Bill Wolfe, co-chairman of the attraction, and chairman of the board of the children's fund, said each year about 3,000 children in Allegheny County experience some form of being homeless.

"Some kids are homeless for a week, some for two years or more," said Mr. Wolfe, 56, of Sewickley. The causes range from domestic problems to natural disasters, he said.

The haunted house, which fronts a new castle-like facade this year, was once the bathhouse of One Hundred Acre Pool, known to locals as Sully's Pool.

The pool, which opened in 1938 during a time of racial segregation, was used by blacks, while whites generally patronized a larger, separate pool nearby.

Sully's pool closed in 1977. In 1992, following extensive volunteer work including rewiring, a new roof and more, the site became home to Phantoms in the Park, a Halloween fundraiser that raised more than $1 million for the Make-A-Wish Foundation.

When attendance began to decline in 2001 from 30,000 to 13,000 visitors per year, "an infusion of new blood," was called for, said ghoul master Ted Sobek, who was instrumental in the start-up of Phantoms and now its successor.

In 2003, he, Mr. Wolfe, and Edward McVeigh donated their money, time and talents to fashion a scarier, more technically savvy, haunted house on the site and called it Hundred Acres Manor.

"It became the new face of horror," said Mr. Sobek, 54, of South Park.

He said the most difficult part of the endeavor "is trying to get the volunteer talent we need to maintain a first-class haunted house."

Among the cast of about 50 seasoned haunters are Gwen Schmidt, 13, and Becca Sayenga, 14, both of Baldwin Borough. Their job is to jump out of the dark, wearing ghostly makeup and scream.

"I like to scare little children and old people, and everyone in between," said Gwen, demonstrating the spirit of the venue.

Among their recent victims were Taylor Olson, 16, of Baden, Beaver County, and Kaitlyn Russell, 15, of Economy Township, who drove an hour with Taylor's father, Jeff Olson, 46, and George Hunt, 28, of the North Side.

"It was the scariest haunted house I was ever at," Kaitlyn said.

Taylor called the 45-minute journey through the house "awesome."

"The maze is really good as it took us forever to find our way out," she said of the labyrinth in which the "lost souls" of the manor are reputed to roam.

Mr. Hunt said he enjoyed the actors in gory costumes who jumped out from the dark and, in a new twist this year, rose from a casket.

The thrill of being frightened also attracted Dustin Bezuk, 22, and family members from Baden.

Mr. Bezuk said he liked the "scary atmosphere" of fog and flashing strobe lights and the actors with chainsaws and wearing hockey masks mimicking the villains of slasher films.

Shena Adams, who conducted psychic readings outside the manor, with half of her fees donated to the two charities, called Hundred Acres Manor "the best haunted house I ever went to."

Ms. Adams, of Jeannette, Westmoreland County, said she especially liked the thick padding through which visitors had to plow their way during one stretch, only to emerge in a dark corridor. Finding one's way in the light-less cavern required navigating the stone-cold walls by touch in search of an opening.

No such travails await Mr. Sobek who, in the best tradition of renowned horror meisters like Dr. Frankenstein, does not subject himself to his own handiwork.

"Honestly, I have never watched horror films or liked haunted houses. I hate being scared," he said.

General admission to Hundred Acres Manor is $13; children younger than 10 get in for $10. For $20 admission, visitors may skip the line. Group rates are available. Only cash is accepted at the door. Discount coupons are available at limited outlets. To pay in advance with credit cards, or for more information, visit www.hundredacresmanor.com or call 412-851-HAUNT.