Hoffmann had known for years that The Expression of the Emotions in Man and Animals was one of the first books to be published with photographs, but he had never actually seen them before. Monochrome plates depicted Victorian artists’ models and inmates of the Surrey Lunatic Asylum in various states of emotion – grief, despair, joy, defiance, terror – for this was meant to be a study of Homo sapiens as animal, with an animal’s instinctive responses, stripped of the mask of social graces. Born far enough into the age of science to be photographed, their misaligned eyes and skewed teeth nonetheless gave them the look of crafty, superstitious peasants from the Middle Ages. They reminded Hoffmann of a childish nightmare – of grown-ups from an old-fashioned book of fairy tales who might come and steal you from your bed in the night and carry you off into the woods.

And there was another thing that unsettled him. The bookseller’s slip had been inserted into the pages devoted to the emotion of fear, as if the sender specifically intended to draw them to his attention:

The frightened man at first stands like a statue motionless or breathless, or crouches down as if instinctively to escape observation. The heart beats quickly and violently, so that it palpitates or knocks against the ribs…

Hoffmann had a habit when he was thinking of cocking his head to one side and gazing into the middle distance, and he did so now. Was this a coincidence? Yes, he reasoned, it must be. On the other hand, the physiological effects of fear were so directly relevant to VIXAL-4, the project he was presently involved in, that it did strike him as peculiarly pointed.