Monsters don't say boo.

They don't run up and shriek in your face.

At least not the zombies, wolves, demons, scarecrows, and the human pigs hiding in the dark at Silverwood Theme Park.

"Monsters lurk in the background, monsters sneak up from behind," said a smiling Nancy DiGiammarco, Silverwood sales and marketing director.

Which is what they'll be doing as Silverwood is transformed into Scarywood Theme Park that opens tonight.

About 130 ghouls and ghosts of "Haunted Nights" underwent 25 hours of training and three nights of run-throughs as they prepare to scare the heck out of 50,000 guests expected to visit through October.

Frightening freaks will be taking devilish delight in their terrible task.

"There are things that work and things that don't work when you're scaring people," said Layne Pitcher, Silverwood spokesman. "You want to make sure they're having a good time, but they are getting scared. There's an art to that."

After three years, they've got terrifying people down to a fine art at Scarywood, which, by the way, isn't for the faint of heart and isn't even recommended for kids 12 and under.

"It's scary," DiGiammarco said. "It's very scary."

A few smaller children passed through the gates to Scarywood last year, and may still be spooked by what they saw and heard.

"They were very frightened," she said.

More startling scenes await this year.

Scarywood, a $2 million investment, has added "Mind Warp," "Blood Bayou," "Terror Canyon Trail," and "Zombiewood Express."

Nightmares await in each. Dark mist and shadows, scream machines, "Freak Farm" and, of course, clowns.

"People tend to be a little freaky of clowns," said John Jachim, Silverwood human resources director.

About 200 people ages 18 and up - 130 actors, a technical crew of 20 to work on makeup and costumes, and a set-up crew of 50 - have been hired for the monthlong production.

DiGiammarco said more monsters, more scare zones, more surprises are in store for Scarywood guests.

"So if people came last year, it will be different," she said.

About 20,000 went through the first year and nearly 40,000 last year. More than 50,000 are expected by the time Halloween rolls around.

Several rides, including Tremors, Corkscrew and Panic Plunge will also be open for guests seeking safety from the walking dead, including some 8-foot tall creepy creatures with blood on their fangs and bulging eyeballs.

Timber Terror will be also going - backward.

"If it wasn't scary enough already, it is now," Pitcher said.

Scarywood will be open 7 to midnight tonight, then Fridays and Saturdays for the next two weekends. The final two weeks of October, it will add Thursdays.

Tickets are available for a discount online at www.scarywoodhaunt.com. Prices range from $19.99 to $29.99, depending on the day.