It was three o’clock in the morning. Along a deserted pavement of RiversideDrive strode briskly a young man whose square-set shoulders and erect poisesuggested a military training. His coat, thrown carelessly open to the coldnight wind, displayed an expanse of white indicative of evening dress. As hewalked his heels clicked sharply on the concrete with the forceful firm treadof the type which does things quickly and decisively. The intense stillness ofthe early morning hours carried the sound in little staccato beats that couldbe heard blocks away. A few yards behind him, moving furtively and n