CHICAGO — I was taking a tour of the Den, a warren of performance spaces carved out of a row of former furniture and clothing stores, when one of my guides opened a door to what I felt sure was a broom closet.

Wrong! It was another performance space. Inside, crews from WildClaw Theater were preparing the tiny black box for that evening’s offering, a play called “Second Skin” that local reviews had called eerie and creepy.

Those were compliments; WildClaw’s aim is to “bring the world of horror to the stage.”

The Den, which blends seamlessly into the workaday commercial strip of North Milwaukee Avenue in the Wicker Park neighborhood here, houses a lot of companies with a lot of aims. I had come that evening to see a revival of “Caroline, or Change” by Firebrand Theater, which calls itself the world’s first professional feminist musical theater company.

But I might as easily have found myself at a historical drama or a director’s showcase or who knows what in the Den’s six other live theater spaces, which range in size from 50 to 150 seats and, in mission, from here to eternity.