It was with an eagerness sternly suppressed that Heldon Foyle took from a messenger the note which he knew contained Grell's advertisement. Although outwardly he was the least emotional of men, he always worked at high tension in the investigation of a case. No astronomer could discover a new comet, no scientist a new element with greater delight than that which animated the square-faced detective while he was working on a case. He drew out the sheet of paper gingerly between his finger-nails, and tested it with graphite. Eight or nine finger-prints, some blurred, some plain, appeared black against the white surface, and he gave an ejaculation of annoyance. "The fools! I warned them to handle it carefully. Now they've been and mixed the whole lot up." He blew down one of the half-dozen speaking tubes hanging at the side of his desk, and gave a curt order. When Green appeared he was engrossed in copying the advertisement on to a writing-pad. He laid down his pen after a while. "That you, Green? Send this up to Grant, and ask him to have it photographed. See if he can pick out any of the prints as being in the records or bearing on the case. Somebody's been pawing this all over, and the prints are probably spoilt. It's been printed out, too, so there isn't much chance of identifying the writing. Anyhow, we'll have a look more closely at it when the finger-print people have done." He bent once more to his desk with the copy of the cipher. He knew the key, and it was not necessary to resort to an expert. By the time the chief inspector came back he had a neatly copied translation on his pad. "Listen to this, Green," he said. "'E. M. Am now safe on board a barge moored below Tower Bridge, where no one will think of looking for me. Have good friends but little money, owing to action of police. Trust, little girl, you still believe in my innocence, although things seem against me. There are reasons why I should not be questioned. Shall try to embark before the mast in some outward bound vessel. Crews will not be scrutinised so sharply as passengers. There are those who will let you know my movements. Fear the police may tamper with your correspondence, but later on when hue and cry has died down will let you know all.'" The two detectives looked at each other. "A barge below Tower Bridge," repeated Green, with something like admiration. "That was a good shot. He might have stayed there till doomsday without our hitting on him, or any one taking any notice of him." "I don't know," said Foyle. "A newcomer on the river would attract attention. These water-men know each other. There's only one way that I can see in which he would avoid being talked about. He is a watchman." "You're right, sir," agreed the other emphatically. "This is a matter where Wrington of the Thames Division will be able to help us. Hope we can find him at Wapping. Shall I ring through?"