Several hours passed before Roy returned, and Captain Hardy began to fear lest, despite the training in the geography of the city, Roy had become confused and gotten lost. Then suddenly the door of the wireless apartment burst open and Roy flew in.
"Chief Flynn told me he thought his men could unravel that message and that I should wait a while," panted Roy, breathless from running up the stairs. "And they did get it. It's what they call a transposition cipher. Here is what it says."
He held out a sheet of paper. On it the letters Roy had picked out of the air were arranged in four lines, as follows:
S R P S T S N
I A O L T M I
X N R E H O N
T S T F I R G
"Read down instead of across," explained Roy.
Captain Hardy studied the cipher a moment more, then read aloud: "Six transports left this morning."
CHAPTER VI
A NEW DANGER POINT
For a moment there was dead silence. Then Captain Hardy spoke. "You have done excellent work, Roy," he said. "Beyond doubt this is a message from a German spy. It is fortunate you caught this particular message, for it proves that, whether there is a leak in the navy department or not, the Germans are watching our ships here in New York. Did you catch the direction this came from, Roy?"