“There is a story that there were once tunnels from St. Mark’s Church to the castle Medvedgrad, where the evil Black Queen threw her lovers from the walls when she was done with them,” Claudia says, eyes glinting. “There are rumored tunnels all over this area, including Visoka Street, where the new president has elected to move her residence.” She smiles mysteriously and opens the door.

I hear it then: the faint pound of bass like a distant heartbeat, as though it might be coming from an apartment one building over.

Or from underground.

We follow her to the cellar, but instead of opening onto a dirty floor, the stair broadens into a tunnel—one hacked out of the original cellar, by the look of it. Electric lights are strung along a ceiling so low that everyone but Claudia has to duck beneath them. I can hear it more distinctly now, the pulse of European trance—coming from somewhere in the distance.

We walk, stooped over, for at least fifty yards until I start to worry that I might seriously have a claustrophobic attack. Just as I’m about to say I want to go back, the tunnel ends at a door. It’s obviously old, bound by iron and guarded by a man in a mask and smart black tuxedo. Without speaking, he fits a key into the lock. The minute he throws the door open on a cavernous underground chamber, we are assaulted by heavy bass. More than that, I actually have to take a step back at the sheer volume of Progeny ahead of us. It hits me like thunder, and I grab for Luka, who steadies me with an arm around the waist.

The man steps aside, head tilted as though he were a butler, but straightens the instant he takes notice of the pendant hanging midway down my chest. At first I think he’s staring at my chest, and have just started to snarl when he steps back and abruptly bows low.

I glance at Luka, who swiftly ushers me through.

“That was weird,” I say, but my words are swallowed by tech-heavy music, the beat interrupting the natural rhythm of my heart as the swarm of bodies begins to jerk, ghoulish beneath a shuttered strobe.

Is it my imagination, or have people turned to stare? One, and then five, and then twenty. They haven’t stopped moving, but the laughter I thought I saw in thrown-back heads gives way to frozen masks swiveled in our direction.

I look around, expecting to see a bar, but there’s no such thing—just a tattoo artist working on a costumed figure reclined in an old barber’s chair in the corner. I get it; the pulse of so many Progeny in one location is more intoxicating than any cocktail, but in none of the usual ways. Goose bumps rise on my arms, climb to my shoulders like an army of ants.