Garstang stopped here and looked at Macdonald with a half smile. “You may wonder why I have inflicted you with that history, but I think you will agree that it makes me a suitable practitioner to treat young Greville. You have told me about his experience in Germany, about his recognition of the language, his memory of a certain house in Cologne. I was born a German: as a child I lived in Cologne.”
“Yes. I appreciate your point,” replied Macdonald, and Garstang went on quickly:
“I knew you would, because you are a reasonable and highly intelligent man: but because detection is your business you are bound to suspect all contacts in your cases, much as a doctor must suspect contacts with infectious disease. I have told you what was the probable reason underlying Harvey’s recommendation of
