“Big enough for a thin man,” said Jenkins, and Lenox nodded without turning.

He was referring to the medium-sized window that Lenox was inspecting, which looked out at a view of the feet walking by on the street, in an almost direct path to the wheels of his own carriage. It was, as Jenkins said, big enough to admit a man or, just as likely, to let a woman out. It was flung open. And on such a cold day.

“Probably too trampled outside to show anything. Scuff marks on the windowsill, which we should bear in mind. Don’t know why they’re there. It’s slick and so is the floor under it, but they probably would be anyway, just from the melting snow. Jenkins,” Lenox said, “have any of the servants been in here?”

“No,” the young inspector said. “Mr. Barnard posted the housekeeper at the door as soon as the body was discovered. And apparently the housekeeper is something of an iron maiden.”

“Do you know what an iron maiden is, sir?” Thomas asked.

Jenkins blushed and didn’t answer; he addressed Lenox. “None of the servants, no, sir.”

“And did Mr. Barnard tell you if he himself touched anything?”

“He said he hadn’t. Only picked up the note, there, on the desk.”

“I see,” said Lenox.

The open window puzzled him, but no doubt it would all come clear. He stepped back into the center of the room and got on his hands and knees. There was nothing on the floors-not even dust, to speak of-under the desk or the bureau, or under the small table, or in plain sight. Except for one thing. In the middle of the room, on the floor just next to the desk, were three or four drops of something. He scratched at one with his fingernail: wax.

He thought about this for a moment, filed it away, and then thoroughly examined the space under the bed, trailing his fingers along the underside of the mattress and shining a candle against every dark corner.