I have a plethora of skills in related disciplines. My skill as an actor enables me to assume disguises so that I could collect evidence which would have been denied me if recognized [MAZA, SIGN, SILV] and to practice malingering so successfully that Watson was convinced that I was about to die [DYIN].

A set of skills enables me to reconstruct stories from the debris which the events leave behind. Hence I have learned to identify the various ashes of cigars and cigarettes, the various perfumes, and the treads of various bicycle tires. The import-ance of communication has resulted in my exploration of secret writings, the decipher-ing of ciphers, the acquisition of foreign languages, the knowledge of English charters, and the idiosyncrasies of typewriters. As a trained athlete, I have certain motor skills of value to a consulting detective - it was my knowledge of baritsu, the Japanese system of wrestling, which enabled me to escape the clutches of Professor Moriarty [EMPT], and my good physical conditioning which enabled me to perch behind a carriage in order to follow a suspect, and my agile fingers which enabled me to crack a safe.

Effective criminologists and criminals both leap on any new technology as soon as it emerges because it gives them an edge. He who hesitates, loses. You will notice that I talk approvingly of a number of recent technologies, and learn not only how to use them but how to counter the abuse of them.

The solutions to many of my cases were due to my understanding and use of a number of recent technologies - of the typewriter [IDEN], of the gramophone [MAZA], of enlarged photographs [LION], of the microscope [SHOS], and in cases too numerous to list of the telegraph. Detectives and criminals have always been with us and always will. The main difference in their eternal duel of wits from generation to generation is in the technologies they use, rather than in the basic principles of detection (and, by implication, of escaping detection) which are expounded here.

New technology changes the rules. For example, the task of assigning someone to copy out the Encyclopaedia Britannica would easily be recognized as a ruse to keep him busy elsewhere with the invention of the photocopier [REDH]. The same invention of course makes the copying of the Naval Treaty a ridiculous task and we would have been less confident that the crisis was over when it was recovered [NAVA]. It is only in such cases, when technology makes a ploy obsolete, that the plots thin.