"P. K." also had an incriminating book--a carefully prepared notebook of his spies and of persons in New York, Boston and other cities who were useful in furnishing him information. In another book he kept a complete record of the purpose and cost of assignments on which he sent his men. He listed in its pages the names of several hundred persons--army reservists, German-Americans and Americans, clerks, scientists and city and Federal employees--showing that his district was large and that his range for getting information and for supervising other pro-German propaganda was broad. For his own direct staff he worked out a system of numbers and initials to be used in communication. The numbers he changed at regular intervals and a system of progression was devised by which each agent would know when his number changed. He provided them with suitable aliases. These men had alternative codes for writing letters and for telephone communication to be changed automatically by certain fixed dates. Always alert for spies upon himself, Koenig suspected that his telephone wire was tapped and that his orders were being overheard. So he instructed his men in various code words. If he told an agent to meet him "at 5 o'clock at South Ferry" he meant: "Meet me at 7 o'clock at Forty-second Street and Broadway." His suspicions were well-grounded, for his wire was tapped, and Koenig led the men who were spying on him an unhappy dance. For example: he would receive a call on the telephone and would direct his agent, at the other end of the wire, to meet him in fifteen minutes at Pabst's, Harlem. It is practically impossible to make the journey from Koenig's office in the Hamburg-American Building to 125th Street in a quarter of an hour. After a time his watchers learned that "Pabst's, Harlem" meant Borough Hall, Brooklyn. He never went out in the daytime without one or two of his agents trailing him to see whether he was being shadowed. He used to turn a corner suddenly and stand still so that an American detective following came unexpectedly face to face with him and betrayed his identity. Koenig would laugh heartily and pass on. Thus he came to know many agents of the Department of Justice and many New York detectives. When he started out at night he usually had three of his own men follow him and by a prearranged system of signals inform him if any strangers were following him.