“It is impossible,” he says. “Out of the question. Absurd.”

I make him wait until I have dunked, bitten off, and chewed my mince pie, brushed crumbs from my lips and chin. The regret in my voice is sweetened by cinnamon and sugar.

“Cruishank tells me the girl spoke the name quite distinctly, and repeated it twice. There cannot be any mistake.”

“Then she is lying!” Swinburne scowls, looks around the room, then at the door that leads to my bedroom. “Is she here?”

“Yes. Sleeping. The poor thing is exhausted. We mustn’t wake her up.”

“Is it true she does not smoke?”

“Oh, she smokes a little. But no more than our sixteen-year-olds. Less than some. It is really quite remarkable. Renfrew ought to be congratulated.”

“Then you do believe her.”

I am amused to see how crushed Swinburne is by this notion: that his favourite pupil should be thought of as a killer. It would be touching if his concern wasn’t born entirely of vanity.

“It really does not matter what I believe. Young Spencer has been named, so he will need to be found and questioned. But there is a larger point to this. Julius is Lady Naylor’s son. He was staying with her when Argyle and Cooper were abducted. It gives the government an excuse to place Lady Naylor under investigation. And her husband, the baron. Officials will be arriving at their house this very night, with a warrant authorising a search.”

I pause, lean forward a little, making sure Swinburne takes note of what I am saying. The man has a thick skull. One has to be emphatic with him.

“You see, we had cause for suspicion before. A letter of Lady Naylor’s was intercepted some weeks ago. She was writing on behalf of the baron, communicating with a scientist on the Continent. As it turns out you know the man in question. I understand he was one of your pupils, what, twenty, thirty years ago?”

Swinburne blanches. “The apostate!”

I do my best not to laugh out loud at the word.

“No more than an errant sheep, surely? Should you not be trying to save him? Return him to the flock? As I understand he was a favourite of yours, once upon a time. You taught him Greek, I believe, at his special request.”

Swinburne’s face is bitter with rancour. “We should never have admitted a foreigner. He fooled me, fooled us all.” He adds, when his slow brain works its way from past to present: “What does the baron want with him?”

“Who can say? The letter was rather cryptic. And we have not been successful in placing a spy in the Naylor household, to provide us with information by other means.”

Swinburne seems unmoved by the idea of spies infiltrating the bosom of the families that rule the land. All he wants to know is: “How hard can it be?”