Frederick sat at his table. He looked out of the window then down at his laptop. It was still dark morning when I walked past. He was wearing green and blue pyjamas and a red and black woolly hat. I waved. He raised a hand in mournful benediction.

A year or so later, Frederick invited me to the launch of his new book. He knew I was a fan though I had never said so and we had never spoken about his work. I never heard a sound up through the floor from his flat except for what I called his Wagner nights and he never complained to me.

His publisher spoke first: Ladies and gentlemen, Frederick will start the evening by reading the very first few paragraphs of his new thriller. You will be the very first people to hear, or read, this new story. There will then be time for questions.

Frederick cleared his throat. “His next victim walked past his window and waved jauntily. He clearly suspected nothing. He thought the killer was his friend. Edinburgh people were like that. They took lack of open hostility as friendship.”

I stopped listening. His next victim?