The creators of Philadelphia's Terror Behind the Walls at Eastern State Penitentiary want visitors to interact with their entertainment.

"You can tweet at Justin Bieber," said creative director Amy Hollaman, "and you can come here and get grabbed by a monster."

New this year is the Machine Shop, where prisoners goad visitors to join them and become "just another cog in the machine," said Hollaman, who promised immersive one-on-one experiences, gruesome industrial scenes and intense startles.

Like last year, visitors will have the option to interact with actors in the exhibit if they opt to be marked with a "blood" X on their cheeks and wear a "tracking device" (glow stick).

Actors in the abandoned prison then know it's OK to touch these participants, separate them from their group, and force them to crawl or climb through obstacles in the attraction. Last year, about two-thirds of visitors opted for this experience, so creators decided to increase the interactivity of the attractions.

Terror Behind the Walls opens Friday and runs through November.