“A convenient doctrine,” Mycroft agreed.

“However, I should say that the author of Testimony may actually believe in his rigmarole. If Crowley is dangerous because shocking and scandalous behaviour is a way of convincing the gullible of his divinity, then this man would be dangerous because he actually believes he is divine.”

“May I assume that your presence here indicates an uncertainty as to the author's identity?”

“There are bits of evidence scattered throughout the thing, but I'm not sure how dependable even those are-he seems very willing to adopt a flexible chronology, even when it goes against good sense. For example, he claims a small meteorite fell into a pond outside the house as he was being born, and that his mother personally supervised its retrieval, but he then says the thing didn't cool for hours. Of course, most religious texts find symbolic truth more important than literal, just as kairos-time-when things are ripe-is more real than chronos-time, which is a mere record of events.”

“Perhaps you might assemble a list of those items with evidentiary potential, so we could reflect on those?”

“Er…”

“You have done so? Very well, proceed.” He clasped his hands behind his back, the cane dangling behind him like an elephant's tail, and listened.

“He draws from the Old and New Testaments, Gnosticism, Buddhism, Hinduism, Zoroastrianism, alchemy, and a variety of mythologies, with an especial interest in the Norse. I'd say he's read a number of works on mysticism, from Jung's psychological theories to William James's Gifford Lectures on The Varieties of Religious Experience. The sorts of books I saw in Damian's house. The author claims, as I said, that he was born during a meteor shower, but there was also a comet in the sky-which could be actual fact, or a sacrifice of accuracy in favour of mythic significance. And come to think of it,” I mused, “that design they use, which I took for a spot-light, could be a stylised comet.

“He has travelled-he mentions France and Italy, the Far East, and the Pacific. He honours and, I think, finds inspiration in the mixed heritage of Britain. In two or three places, he employs artistic metaphors. And, I, well…” I exhaled. “There are eight drawings by Damian in the book.”

We navigated the crossing of Piccadilly and Park Lane and were well into Hyde Park before Mycroft spoke. What sounded like a tangent went in fact directly to the heart of what I had been telling him.

“My brother permits few people inside his guard. Four people in his first sixty-three years, I should say: myself, Dr Watson, Irene Adler, and you. For those inside his affections, Sherlock's loyalty is absolute. In another man, one might call it blind. Any one of us four could commit cold-blooded murder, in Trafalgar Square, in broad daylight, and he would devote every iota of his energy and wit to proving the act justified.”

“And now there are five.”

“I have not seen my brother and my nephew together, but I should not be surprised to find Damian added to the fold.”

We paced in silence for a time, until I responded with an apparent tangent of my own.

“Has Holmes told you what happened in San Francisco this past spring?”

“He mentioned that you had received unexpected and disconcerting information concerning your past.”

“I doubt he couched it that mildly. I discovered that pretty much everything I thought I knew about my childhood was wrong. That after my family died, I shut my life behind a door and forgot it. Literally. ‘Disconcerting’ isn't the word-I felt as if the ground beneath me had turned to quick-sand. It has left me doubting my own judgment. Doubting whether or not to trust anyone else.”

“Including Sherlock.”

“Him I trust, if anyone. And yet, I can't help thinking that Damian's mother deftly outflanked him. Twice.”

“Yes, although when Sherlock met her, he assumed her to be a villain, when in fact she was not. That is quite a different thing from falling for the schemes of a villain one believes innocent.”

“You think he could not be deceived by Damian?”

Another lengthy silence, then he sighed. “You think Damian wrote this book?”

“Do you know his birthday?”

“The ninth of September, 1894.”

The Perseid meteors would have been finished; I should have to find if there were any comets that year. “What about his mother? Did she die on a full moon?”

“She died in June 1912, but I do not know the precise day. This is in the book?”

“To answer your question, I hope Damian had nothing to do with Testimony beyond the drawings. But if I can't trust my instincts, I have to use my head. And my head tells me that there are points I cannot ignore.”

“Perhaps you had better list them.”

“The moon, to begin with: It's in nearly all his paintings, two men near him died around the full moon, and now his wife. The house where he was born had a pond-I've seen a drawing. The author of Testimony had no father and was raised by women; as an adult he was badly injured, went into some sort of a coma, and came out with what he calls ‘the eternal stigmata of divinity.’ Damian was raised without a father, he was injured in the trenches, and the scars on his head might be considered Christ-like. The man in Testimony then went through a period of darkness before finding a ‘guide,’ who took his hand and showed him the way ahead. After Damian killed his fellow officer, he was sent to the mental hospital in Nantes; there he met André Breton, who introduced him to automatism. Damian's paintings and Testimony are both permeated with mythological elements, particularly the Norse god Woden. And, he has a self-portrait showing Holmes, Irene Adler, and himself with a sun, a moon, and a comet over their heads.

“Damian explains his art by saying that he became sane by embracing madness, finding beauty in obscenity. The book is both mad and obscene.

“Finally, there is the child's name. He and Yolanda named her Estelle, or star. Testimony makes much of stellar influence.”

“Possibly. On the other hand, Estelle was also the name of my mother. Our mother.”

I turned to stare at him. “Really? I never knew that. Would Damian have known?”

“One should have to ask Sherlock.”

And asking Sherlock would mean opening up this entire can of worms and setting it in front of him with a fork. Neither of us wished to do that without some kind of actual evidence.

We had crossed the Serpentine, where the good cheer of the crowd at the tea house made a mockery of what we were saying.

“What of evidence to the contrary?”

He was not about to admit that my damning list of links between Damian and the book was in any way evidence, certainly not for any court of law. Nonetheless, damning it was.

“First and foremost, it's nonsense. Intellectual trash. I can't think Damian's mind works that way.”

“Unless,” Mycroft said, playing devil's advocate, “the nonsensical nature of the writing is a deliberate choice, aimed at catching the imagination of a certain audience.”

“It's not just intellectual snobbery speaking when I say that it's deeply troubling, and frightening, to think that Holmes' son could produce such a thing.”

“So say the families of any of the world's spectacular murderers.”

“All right, what about this: Holmes has considered the possibility that Damian killed Yolanda, and rejected it.” Mycroft was silent, which constituted an agreement that this was a heavy weight on the side of innocence. “There is also the clothing Yolanda was wearing-an ugly frock, and shoes and silk stockings far too large for her. They were purchased by Millicent Dunworthy, under orders from someone, but there is no indication that she was making the purchase for Damian. In any case, he would have known the size of his wife's feet and the length of her legs.”