“So you are truly a consulting detective?” I said.

“The only one in London, or perhaps, the world,” said my friend. “I do not take cases. Instead, I consult. Others bring me their insoluble problems, they describe them, and, sometimes, I solve them.”

“Then those people who come to you-”

“Are, in the main, police officers, or are detectives themselves, yes.”

It was a fine morning, but we were now jolting about the edges of the rookery of St. Giles, that warren of thieves and cutthroats which sits on London like a cancer on the face of a pretty flower-seller, and the only light to enter the cab was dim and faint.

“Are you sure that you wish me along with you?”

In reply my friend stared at me without blinking. “I have a feeling,” he said. “I have a feeling that we were meant to be together. That we have fought the good fight, side by side, in the past or in the future, I do not know. I am a rational man, but I have learned the value of a good companion, and from the moment I clapped eyes on you, I knew I trusted you as well as I do myself. Yes. I want you with me.”

I blushed, or said something meaningless. For the first time since Afghanistan, I felt that I had worth in the world.

2. The Room

VICTOR’S VITAE! AN ELECTRICAL FLUID! DO YOUR LIMBS AND NETHER REGIONS LACK LIFE? DO YOU LOOK BACK ON THE DAYS OF YOUR YOUTH WITH ENVY? ARE THE PLEASURES OF THE FLESH NOW BURIED AND FORGOT? VICTOR’S VITAE WILL BRING LIFE WHERE LIFE HAS LONG BEEN LOST: EVEN THE OLDEST WARHORSE CAN BE A PROUD STALLION ONCE MORE! BRINGING LIFE TO THE DEAD: FROM AN OLD FAMILY RECIPE AND THE BEST OF MODERN SCIENCE. TO RECEIVE SIGNED ATTESTATIONS OF THE EFFICACY OF VICTOR’S VITAE WRITE TO THE V. VON F. COMPANY, 1B CHEAP STREET, LONDON.

It was a cheap rooming house in Shoreditch. There was a policeman at the front door. Lestrade greeted him by name and made to usher us in, and I was ready to enter, but my friend squatted on the doorstep, and pulled a magnifying glass from his coat pocket. He examined the mud on the wrought iron boot-scraper, prodding at it with his forefinger. Only when he was satisfied would he let us go inside.