She knelt down next to Elizabeth. “You need to go get an adult,” she said to the roommate, who stiffened. “Look, believe what you will about my motives, but either way, this crowd will make sure I don’t hurt your friend. Okay? So go get help and let me work. I’ve been trained for this kind of situation.”

“CPR?” the girl asked unsteadily.

Holmes’s smile was mirthless. “Something like that.”

“What do you need me to do?” I asked.

“I need you to hold her mouth open.” She tilted Elizabeth’s head back. “Keep her steady. Do you see it there, in her throat?”

The skin of Elizabeth’s neck was raised and ridged, the unmistakable sign of an object lodged there. With gentle hands, I pulled her chin down until her lips fell apart.

This girl had asked me to the dance. Maybe she’d even wanted something like this: the pads of my fingers against her lips, the shallow breathing, the two of us hitched up in the dark. My stomach roiled. All this—all this was so completely wrong.

“Her body’s in shock,” Holmes said calmly, reaching down into the hollow of Elizabeth’s throat with pincer-like fingers. I shut my eyes against it. The girl thrashed and gurgled under my hands.

“Good girl,” Holmes murmured, “good girl,” and when I opened my eyes again, she was holding a gleaming blue diamond up against the moonlight.

It gleamed because it was covered in Elizabeth’s blood.

I swallowed down bile. Behind me, someone threw up into the grass.

“It’s ‘The Adventure of the Blue Carbuncle,’” Holmes murmured.

“I know,” I said as Elizabeth took a jerking breath.

“You.” Holmes tossed the diamond to a boy in the crowd. “Take this thing. It’s plastic, so don’t bother stealing it, but I’m sure the police will want to see it anyway, and as you’re all so keen to cast suspicion on me I’d rather not be held responsible for its safekeeping. Where’s Randall? You. Fetch him. Can’t you see that this girl has been manhandled by a rugby player? Look at those footprints. Look at her dress. I saw them dancing. Find him. I need to know if this was consensual. The sex, you idiot, not the paste diamond stuffed down her craw—yes, of course she’s had sex, or at minimum a very athletic snog. Look at the marks on the ground, are you blind? And where on earth are the chaperones? What about that bloody nurse?”

“Here,” a harried voice said. It was the first time I’d seen Nurse Bryony outside the infirmary; her party dress fit her so tightly that it looked painted on. She smiled reassuringly at me, but I looked away. I didn’t deserve reassurances.

“Tend to her, will you?” Holmes told the nurse, straightening. “Where is that ambulance?” She shaded her eyes against the nonexistent light.

“Holmes.”

“Not now, Watson.” She plucked another boy’s phone out of his hands, dialing 911 as he sputtered at her in protest. “You talk, then,” she said to him, handing it back. “Be of some use.”

“Holmes,” I said, more urgently.

I’d caught a glimpse, at the very edge of the crowd, of the drug dealer’s thick blond hair.

She followed my gaze and made a startled noise. “I didn’t think we’d see him again.”

“Well.” I got to my feet. “What now?”

“Don’t look at him directly.” But it was too late. As she spoke, he turned in a way he must’ve thought unobtrusive, beginning to melt into the darkness.

“We’re going to have to chase him again,” I said. God, my legs hurt at the thought.

That quicksilver smile. “On your marks.”

The dealer threw a glance behind him, and took off at a run.

We bolted through the crowd. Some ducked out of our way; others tried to pull us back, thinking we were fleeing the crime scene. We were, but not in the way they thought. There: he was pelting across the flat green expanse, headed straight for Stevenson Hall. Lots of the underclassmen girls lived there—Holmes did, and Elizabeth did too, and I couldn’t think of any reason why he’d be heading there except to do more damage. Guilty people ran. He had to be guilty. I pushed myself to run harder, but I was already topped out. Sirens wailed—the soundtrack of my ridiculous life—and Holmes’s dress ahead of me caught the red-and-blue light, strangely beautiful. She was faster than me, smaller, leaner. She was just beginning to gain on him when three cruisers and an ambulance pulled off the road and onto the grassy quad beside us.

“Some help here,” Holmes yelled as a group of policemen clambered out. The EMTs were already unloading a stretcher from the ambulance.

“Is that Charlotte Holmes?” It sounded like Detective Shepard. I spared a look and spotted a lone man not in uniform. “Stop! What are you doing? James! Jamie Watson!”

Neither of us slowed down in the slightest. So Shepard took off after us.

The policemen gave confused chase behind him, cursing and breathing heavily. Up ahead, the dealer rounded the corner of Stevenson Hall and disappeared from view.

“The access tunnels,” Holmes called. “There’s an entrance, there—it’s that half door; it has a key code—”

I pushed the building’s tangled ivy out of the way as she tapped out the code.

“You have about two and a half seconds,” I said, “before the police brutality begins.”