The task of keeping watch of Koenig's movements required astute guessing and tireless work on the part of the New York police. So elusive did he become that it was necessary for Captain Tunney to evolve a new system of shadowing him in order to keep him in sight without betraying that he was under surveillance. One detective, accordingly, would be stationed several blocks away and would start out ahead of Koenig. The "front shadow" was signaled by his confederates in the rear whenever Koenig turned a corner, so that the man in front might dart down a cross-street and manoeuvre to keep ahead of him. If Koenig boarded a street car the man ahead would hail the car several blocks beyond, thus avoiding suspicion. In more than one instance detectives in the rear, guessing that he was about to take a car, would board it several blocks before it got abreast of Koenig. His alertness kept Detectives Barnitz, Coy, Terra, and Corell on edge for months. It was impossible to overhear direct conversation between Koenig and any man to whom he was giving instructions. Some of his workers he never permitted to meet him at all, but when he kept a rendezvous it was in the open, in the parks in broad daylight, or in a moving-picture theatre, or in the Pennsylvania Station, or the Grand Central Terminal. There he could make sure that nobody was eavesdropping. If he met an agent in the open for the first time he gave him some such command at this: "Be at Third Avenue and Fifty-ninth Street at 2:30 to-morrow afternoon beside a public telephone booth there. When the telephone rings answer it." The man would obey. On the minute the telephone would ring and the man would lift the receiver. A strange voice told him to do certain things--either a definite assignment, or instructions to be at a similar place on the following day to receive a message. Or he might be told to meet another man, who would give him money and further orders. The voice at the other end of the wire spoke from a public telephone booth and was thus reasonably sure that the wire was not tapped. And Koenig trusted no man. He never sent an agent out on a job without detailing another man to shadow that man and report back to him in full the operations of the agent and of any persons whom he might deal with. He was brutally severe in his insistence that his men do exactly what he told them without using their own initiative. Koenig had spies on every big steamship pier. He had eavesdroppers in hotels, and on busy telephone switchboards. He employed porters, window-cleaners, bank clerks, corporation employees and even a member of the Police Department.