When I arrived at her lab the next day after classes, Detective Shepard was stepping out of the door. I hadn’t known that he could interrogate either of us without a parent there, but he must have found a way to talk to Holmes.

“Jamie,” he said heavily. “I’ll see you and Charlotte on Sunday night at your father’s house. We’ll talk then.” With that, he fixed me with a pitying look and took off down the hall.

“Wait, you’re coming to that?” I called after him, but he didn’t respond.

Inside, on the love seat, Holmes was wrapped up in an avalanche of blankets. She looked like one of those Russian nesting dolls, like she was the smallest Holmes in a series.

Whatever words she’d exchanged with Shepard, they’d left her in a mood.

“Why did you let him in? What was that about, exactly?”

“Nothing.”

“Nothing,” I repeated. “I thought you were giving him Dobson’s infirmary records.”

“He already had them, of course,” she said. “He chided me for breaking and entering, and left.”

“So Dobson did go to have his symptoms treated.”

“He went to the infirmary often,” she said. “Mostly rugby-related injuries, Shepard said. He said they’d tested his hair for arsenic and found it, and didn’t need any of my proof. Then he asked me to identify all the vials on my poisons shelf. And then he left, saying he’d see us soon, in a voice I think he thought was threatening. Amateur.”

“Wait, back up. You let the detective in here. You let him look at your poisons shelf.”

“Yes.”

“Poisons.”

“Yes.”

“And there’s arsenic on that shelf?”

“Yes.”

“And he’s interrogating us again this Sunday,” I said, feeling sick.

“Yes,” she said, drawing the word out like I was an idiot.

I stared at her for a long minute. She had to know something she wasn’t telling me. “Right. We need to make a list of possible suspects. We need to find something we can give them. Anything to make you—us—look less guilty.”

Turning away, I taped a sheet of butcher paper to the side of her bookcase and wrote “suspects” at the top.

“Watson,” she said, “you don’t have any suspects.”

I glared at her. She brought her cigarette to her lips and took a long drag. We’d reached an unspoken agreement: she’d dump the pill bottles, and I’d stop checking for them. That’s how I chose to read the new and constant presence of a lit Lucky Strike in her hand—that she was trying out a drug that wouldn’t kill her, at least not as quickly.

But all that smoke meant the unventilated lab was starting to resemble some toxic back room of hell, edging me ever closer to my breaking point. And still Holmes sat, and smoked, and told me nothing.

“What about the person who checked out that copy of The Adventures of Sherlock Holmes from the library? There have to be records.”

“Correction. That particular copy was new and had never once been checked out from the library. Someone stole it off the shelf,” Holmes said. “Currently, the library database has it listed as ‘missing.’ And as the physical copy is in police possession, I have no way of examining it.”

“What about enemies? We could list Dobson’s enemies.”

“Go on, then. Put down every girl at the school.” Her eyes went dark. “Though I can tell you that, from the research I did last year, I know I’m the only one who had a . . . run-in with him.”

I swallowed. “We could list our enemies, then.”

“You haven’t got any enemies.”

“I’ve got ex-girlfriends,” I countered. “English ones. American ones. Scottish ones. I could so see Fiona with some sort of tartan apothecary box for her poisons . . .” Although it was hard to actually imagine Fiona doing anything but dumping me in front of my entire class.

Holmes raised an eyebrow. “No,” she said, and exhaled.

I kept myself from pulling the cigarette from her hand and grinding it out on the floor.

“I haven’t been sleeping,” I told her, “because I am worried that either you, or I, or some innocent lunch lady will bite it now that we’ve gotten ourselves a murderous fan club. So give me a hand, will you?”

Her eyes narrowed in concentration. “The Marquess of Abergavenny,” she said, finally. “I set fire to his stables when I was nine.”

“Fine,” I said, and then, in a smaller voice, “Can you spell that?”

She ignored me. “I suppose you could add Kristof Demarchelier, the chemist. The Frenchman, not the Dane. And the Comtesse van Landingham—Tracy never liked me. She didn’t like my brother Milo either, for that matter, but then he did break her heart. Oh, and the headmistress of Innsbruck School in Lucerne, for beating her so often in chess, and the champion table tennis player Quentin Wilde. I suppose you might as well add his teammates Basil and Thom. Thom with an ‘h,’ of course. Though I can’t remember their surnames. Strange.”

“Is that it? Or are there peers and MPs that you’re forgetting? Maybe a crowned head or two?”

She took a puff that sent her into a coughing fit. When she regained her composure, she said, “Well, there’s August Moriarty,” as if that shouldn’t have been the first name out of her mouth.