"The pocket-book contained a secret code," explained Selwyn. "It has been partly deciphered, and is proved to be a means of communication between someone on board the ship and the U-boats. I explained how I found it, and offered to produce you chaps as witnesses, but the Major was awfully decent about it. He means to find the owner, and if necessary is going to interrogate every man who went into that stokehold. Hallo, they've rounded up our immediate predecessors already."