“We’ve had an anonymous tip-off. But I wouldn’t get overexcited, madame. These people are normally time-wasters.”

“Really?” said Sister Marguerite. “That seems a bit harsh. Surely we can be a bit excited. Will it go all the way to Istanbul by train, do you think?”

Commandant Le Goff snapped Max’s case shut. “Good day, Sister. Good day, mademoiselle.” The other two officers took their cue, and shuffled forward to stare meaningfully at the next row of people.

“Is that all?” Marguerite exclaimed. “The heartbreak diamond is tiny. I could be hiding it in my wimple.”

The Commandant’s egg face was starting to twitch a bit, as though it might hatch at any moment. “That will be all,” he said. “Thank you.”

“You don’t want to double-check the wimple?”

“Really,” said the Commandant irritably, “I think the wimple is neither here nor there.” And he moved on to check the bags of nice, normal people who didn’t bother him with questions and unusual headwear.

“Well,” said Marguerite to Max, in a loud stage whisper, “I don’t think that was very professional. I could be hiding half the Louvre in my shoes.”

Max thought that this was unlikely, even in Marguerite’s enormous shoes. But she was too busy watching Commandant Le Goff to object. He was scrambling hastily through the remaining bags, asking people vague questions and looking at his watch. He really didn’t seem to be doing the job very thoroughly at all. He made it to the end of the carriage at top speed, thanked them for their time, announced that his junior officers would be staying on the train and should be alerted to anything suspicious, then ducked out of the carriage and off the train at double speed. As he hurried down the platform, the officers at the doors flocked after him. They were gone as swiftly as they had arrived.

The two officers left on board nodded importantly at everyone, and fiddled importantly with their hats. Then when that was done, they marched off importantly to fiddle with their hats in the other carriages as well.

Max scribbled all this down in her notebook, and twirled a plait as she thought it all over. “Sister,” she began, “do you think there could really—” but then she was distracted by another tut-PFFfff. She thought Le Goff had come back. But the man who entered was very much not Le Goff.

He was a young man with flyaway hair, wearing a tweed jacket and the amazed smile of a man who is half an hour late for his train and finds it hasn’t left the station yet. He made his way down the aisle, but did a terrible job of it, tripping over and bumping into everything available, squinting at all the seats as he went.

He stopped and had a really good squint at the pair opposite Max and Marguerite. “Excuse me,” he said, “is this seat ninety-eight?”