"That's so. Since then, I reckoned that they were getting after him _here_, but we were more likely to hold them up if they didn't know we knew. That's why I called out to show I thought it was Pepe who was in the shack." "Very well," said Jake. "There's nothing more to be done in the meantime, but you'd better tell me if you find out anything else." Payne went away and when Dick came in Jake took him into his room and indicated the blotter. "Have you torn off the top sheet in the last few days?" "I don't remember doing so, but now I come to look, it has been torn off." "What have you been writing lately?" "Orders for small supplies, specifications of material, and such things." "Concrete, in short?" Jake remarked. "Well, it's not an interesting subject to outsiders and sometimes gets very stale to those who have to handle it. Are you quite sure you haven't been writing about anything else?" "I am sure. Why do you ask?" "Because, as you see, somebody thought it worth while to steal the top sheet of your blotter," Jake replied. "Now perhaps I'd better tell you something I've just learned." He related what Payne had told him and concluded: "I'm puzzled about Oliva's motive. After all, it could hardly be revenge." "No," said Dick, with a thoughtful frown, "I don't imagine it is." "Then what does he expect to gain?" Dick was silent for a few moments with knitted brows, and then asked: "You have a Monroe Doctrine, haven't you?" "We certainly have," Jake agreed, smiling. "We reaffirmed it not long ago." "Roughly speaking, the Doctrine states that no European power can be allowed to set up a naval base or make warlike preparations in any part of America. In fact, you warn all foreigners to keep their hands off?" "That's its general purport; but while I support it patriotically, I can't tell you exactly what it says. Anyhow, I don't see what this has to do with the matter." "Nor do I, but it seems to promise a clue," Dick answered dryly. He frowned at the blotter and then added: "We'll leave it at that. I've some vague suspicions, but nothing to act upon. If the thing gets any plainer, I'll let you know." "But what about Payne? Is he to hang around here nights with his gun?" "No," said Dick, "it isn't necessary. But there'd be no harm in our taking a few precautions."