The program has been running many nights since mid-September and lasts this year until November 10th. Organizers say it's their biggest and scariest ever.
Designer Jason Ohlsen told Action News a new experience called "Detritus" has visitors walk unescorted down a darkened cell block into a courtyard.
They go from there to the prison's greenhouse, where vines will seem to come to life. On any given night, upwards of 200 staff and actors will be on hand...many of them costumed personnel who seem to come out of nowhere and, well, scare you.
Many of the professional actors have been participating for more than a decade. The "scare" level is intense enough that children under 12 are discouraged. Having said that, Sunday nights see more families visit. Kids who find the experience uncomfortable may say "monster be good" and the actors are trained to tone things down...a bit.
It's possible to walk up the night of a show and obtain tickets, but you'll always find it cheaper to buy online, in advance. There are also special shows. One VIP experience allows four visitors to go through: terror" alone...no one else on the premises.
They also get a tour of the prison as a historic site, then enjoy a complete dinner at Jack's Firehouse across the street.
You can find details of all the options and order tickets at Eastern State Penitentiary.
"Terror Behind The Walls" is the single biggest source of income for Eastern State Penitentiary, a 200-year-old prison that influenced both the theory of prison design and the philosophy of the American criminal justice system.
Organizers hope visitors to the Halloween season event will be interested enough to come back for a daytime prison tour and perhaps get involved in the massive preservation effort.
Memberships are available and donations are tax-deductible.