My skin crawled. “You’re Gretchen, right?” I asked, hoping she’d point toward who was.

“Gretchen?” She shook her head. “I’m Hanna. Marie-Helene was calling us her mädchen—her girls. Is that what you were thinking of?”

I was stumbling into some sleazy party based on something I didn’t actually hear in a bar.

Marie-Helene pulled me up the steps to the brick building’s door. “Our destination awaits,” she said, ushering us in.

The main floor was surprisingly dark and quiet, but it wasn’t our “destination.” Without turning on a light, Hanna felt around to her right until she found a doorframe. “Down these stairs,” she whispered. “Turn on your phone if you need light.”

At the bottom of the stairs was a door, and beyond that door was a cavern.

Marie-Helene and her friends made a beeline for the bar in the corner. I was left standing with one hand on my hat, taking it all in.

The cavern didn’t feel natural. The walls were lined with tile, and the ceiling had a perfect arch that meant it was man-made. A damp, sharp smell hung in the air. It took me a moment to place it as chlorine. I pushed past a knot of people and saw its source—a massive pool in the center of the room. One girl kicked her legs on an inflatable swan, holding her martini glass safely above her head. A pair of boys were dangling their feet in the water as they made out. Everywhere, a dim, fractured sort of light speckled people’s faces, speckled the walls.

Without thinking, I turned to clock Holmes’s reaction. It was what I always did in these down-the-rabbit-hole situations. It took me a minute to find her, still standing up on the now-deserted staircase, and I caught the end of a transformation—a subtle one, this time. Somewhere along the way, she’d lost the fanny pack. One hand was hastily unbuttoning her cardigan, and the other was tapping some kind of lip gloss on her mouth. The whole process took less than a minute, and when she stepped down into the party, she was wearing a little black dress and a haughty expression. In this light, her mouse-brown hair looked soft and warm. She was recognizably the same girl as she was in the Old Metropolitan, and she wasn’t at all.

On her tottering heels, she padded up between me and August. “Boys?” she asked, and on her cue, we took her elbows and led her into the party.

I leaned down to whisper in her ear. “Is this the part where we share information? Because I know how you came up with the Old Metropolitan. It’s just something you’ve overheard back in Sussex. No magic there.”

She glanced up at me. “It’s all magic, Simon,” she said, “if I’m to believe what you write about me.”

“He’s your biographer?” August asked. “Like Dr. Watson? Jesus, that’s ador—”

“It is not adorable.” I pulled us to a stop at the pool’s edge. Beside me, Holmes squinted across the room. The light from the water was freckling her cheeks, and I resisted the urge to touch her face, to see if I could make them scatter. “Of course I know it isn’t magic. I’ll prove it. Do you want me to tell you what you’ll do next?”

She smiled, almost imperceptibly. “Go on, then.”

I gave myself a second to look around the party. Hanna had been right. Here and there someone broke the mold, but really there were two kinds of people here: college-age girls and men who gleamed with that particular sheen of money. The girls were mostly in tiny dresses, but the men were all dressed differently, some in suits and some more like artists, some in rumpled black and some neatly pressed. Some had a dancer’s build, or the anxious stare of a writer.

Next to us, a girl was flicking through what looked like slides of her work on her iPhone. “As you can see,” she was saying, “I’m an excellent candidate for your opening.”

Immediately, Holmes turned her head to listen.

Focus, I told myself, and looked around the room again. I was not going to make a fool out of myself, not with Blond Gaston over her other shoulder.

“There’s a man in the corner,” I said finally. “The one with the scarf and the round glasses. He’s the best candidate for Leander’s professor contact. What was his name? Nathaniel?”

Beside me, Holmes made a humming sound. She wasn’t looking at him; her attention was fixed on the conversation behind us. “Explain your reasoning.”

It suddenly seemed so important for me to be right. To get her to look at me, really look at me, the way I needed her to. Squinting, I considered the man in question, who was telling a story with his hands. “His body language. He seems much more relaxed than the other men here. He’s not jockeying for status or trying to get laid; he looks like he’s catching up with friends. And the people around him are at ease, too. Look at the guy next to him—he’s what, eighteen, and he just whacked Nathaniel on the arm while he was talking. Now he looks shocked, probably at his own gumption, and everyone’s laughing. They’re all comfortable with each other. He’s their authority figure, but they like him.”

With the calm electricity of a hunting dog in a field, Holmes stared down the man in the suit. The only problem was that it was a different man in a different suit.

“Plus he’s handsome,” I said desperately, trying to refocus her, “and people meet at the Old Metropolitan to walk down here on Saturday nights, and you said your uncle was involved with someone here, someone in this scene. Does Leander like redheads?”