SEATED OPPOSITE ME in the railway carriage, the elderly lady in the fox-fur shawl was recalling some of the murders that she had committed over the years.

“There was the vicar in Leeds,” she said, smiling a little as she tapped her lower lip with her index finger. “And the spinster from Hartlepool whose tragic secret was to prove her undoing. The actress from London, of course, who took up with her sister’s husband just after his return from the Crimea. She was a flighty piece so no one could blame me for that. But the maid-of-all-work in Connaught Square, I rather regretted killing her. She was a hard-working girl of good Northern stock, who perhaps didn’t deserve such a brutal ending.”

“That was one of my favourites,” I replied.

“If you ask me, she got what was coming to her. She read letters that were not hers to read.”

“I know you, don’t I?” she asked, sitting forward now, narrowing her eyes as she examined my face for familiar signs. A sharp combination of lavender and face cream, her mouth viscous with blood-red lipstick. “I’ve seen you somewhere before.”

“I work for Mr. Pynton at the Whisby Press,” I told her. “My name’s Tristan Sadler. We met at a literary lunch a few months ago.” I extended my hand and she stared at it for a moment, as if unsure what was expected of her, before shaking it carefully, her fingers never quite closing on my own. “You gave a talk on untraceable poisons,” I added.

“Yes, I remember it now,” she said, nodding quickly. “You had five books that wanted signing. I was struck by your enthusiasm.”

I smiled, flattered that she recalled me at all. “I’m a great admirer,” I said, and she inclined her head graciously, a movement that must have been honed over thirty years of receiving praise from her readers.