“Oh, no. I delivered it to the cutter, Hendrik Jonkheer, yesterday. Today I went back to watch the start of the cutting. Mrs Upwater went with me. I’d brought her along, for a little holiday. And — tell Mr Templar what happened, Mabel.”

“Mr Jonkheer looked Mr Upwater straight in the eye,” said Mrs Upwater, “and told him he’d never seen him before and he certainly hadn’t brought him any diamond.”

Something like a phantom feather trailed up the Saint’s spine, riffling his skin with ghostly goose-pimples. And on the heels of that psychic chill came a warm pervasive glow of utter beatitude that crowned his recent feast more perfectly than the coffee and Napoleon brandy which he had not yet touched nor would ever do. His interest was no longer polite or even perfunctory. It had the vast receptive serenity of a cathedral.

For just as a musician would be electrified by a cadence of divine harmonies, so could the Saint respond to the tones of new and fabulous adventure. And about this one, he knew, there could be nothing commonplace. Suddenly he was humbly grateful for his ambiguous reputation, for the little difficulty at the hotel, for the resultant gossip, for the extravagant bonus which it had brought him. Because in a few simple unmistakable words the prosaic Mr and Mrs Upwater had placed in his hands the string to a kite of such superlatively crooked design that its flight, wherever it led, could bring only joy to his perversely artistic soul — a swindle of such originality and impudence that he contemplated it with an emotion bordering upon awe.

“That,” said the Saint at length, with transcendent understatement after so long a pause, “is a lulu.”

“I can’t get used to it yet,” Mr Upwater said dazedly. “He stood there, Mr Jonkheer did, looking straight at me just like I’m looking at you, only as if he thought I was a lunatic, and said he’d never set eyes on me before in his life. He almost had me believing I’d gone out of my mind. Only I knew I hadn’t.”

“It’s just like that story,” Mrs Upwater said. “You must know the one. About the girl and her mother who go to a hotel in Paris, and the mother’s sick, so the daughter goes out to get her some medicine, and when she gets back everybody in the hotel says they’ve never seen her before, or her mother, and when she goes to the room where she left her mother it’s a different room, and there’s nobody there.”

Simon nodded, almost in a trance himself.

“I know the story,” he said. “It turns out that the mother had the plague, or something, doesn’t it? And they got rid of her and tried to cover it up because they didn’t want to scare away the tourists... But this is a new twist!”

“That it is,” said Mr Upwater gloomily. “Only diamonds don’t get any disease. But they’re worth a lot of money.”