"Tell me, did he commit suicide, or was he killed in his room; and if so how a murderer killed and vanished leaving no trace within a minute?" The Dilettantes Club is a gathering of five savants who dine once a fortnight in Soho, and debate any problem besetting mankind. One evening, into this distinguished company, there intrudes a Professor of Logic and Philosophy, an odd little man. The Assistant Commissioner of Scotland Yard is one of...