"Okay. Let’s take it from the top. Azure message goes from Tokyo to Rabaul," Waterhouse says, drawing a heavy line down the chalkboard joining those two cities. "The next day, a message in some other crypto system—one that we have broken—goes from Rabaul to a submarine operating out of a base here, in the Moluccas. The message states that the submarine is to proceed to an outpost on the north coast of New Guinea and pick up four passengers, who are identified by name. From our archives, we know who these men are: three aircraft mechanics and one mining engineer. A few days later, the submarine transmits from the Bismarck Sea stating that it has picked those men up. A few days after that, our waterfront spies in Manila inform us that the same submarine has showed up there. On the same day, another Azure message is transmitted from Manila back up to Tokyo," Waterhouse concludes, adding a final line to the polygon, "closing the loop."