Detective-Constable Hilary Vanjohn, though concerned to manifest the nonchalance which he thought proper at once in a police officer and in a graduate of Oxford (B.N.C.), really was vastly excited by his first experience of a murder case. It was for that reason, maybe, that he permitted himself the gesture of placing the barrel of his fountain-pen under his nose and attempting to support it by an outward-curled upper lip. The effect, of course, was to give him the appearance of twirling a strange green moustache with ebony ends. It chanced just then that the superior to whom he was acting, as it were, as amanuensis, Chief Detective-Inspector Archibald Burford, glanced in Hilary’s direction. Their glances met. And Detective-Constable Vanjohn, aware that the dreamily absent look in the sea-grey-blue eyes of his chief momentarily gave place to an amused gleam, hastily snatched the pen away from under his nostrils, felt a sense of heat about his ears and jowls, and became frowningly interested in the notes he had been making. It was with the utmost effort that he forbore giving a quite unnecessary cough.