Isaac was a fortnight shy of his forty-sixth birthday. Since his hair had gone white, his appearance had changed very little; he never stopped working to eat or drink and so he was as slender as he had always been, and the only symptom of age was a deepening translucency of his skin, which brought into view tangles of azure veins strewn around his eyes. Like many College dwellers he found it a great convenience to hide his clothing – which was always in a parlous state, being not only worn and shabby but stained and burnt with diverse spirits – underneath an academic robe; but his robe was scarlet, which made him stand out vividly at the College, and here in London all the more so. He did not wear it in the street, but he was wearing it now. He had not affected a wig, so his white hair fell loose over his shoulders. Someone had been brushing that hair. Probably not Isaac. Daniel guessed Fatio.