"You know the game," he remarked, laying a thick forefinger on the diagonal line bisecting the page. "All I had to do was to test the letter by drawing that line across it from corner to corner. Read the words that the line cuts through. Can you beat it?"
Vaux and Miss Erith bent over the letter, read the apparently innocent message it contained, then read the words through which the diagonal line had been drawn.
Then Cassidy triumphantly read aloud the secret and treacherous information which the letter contained: "SEVEN UNITED STATES TRANSPORTS TO-DAY NEW YORK (BY THE) NORTHERN ROUTE. INFORM OUR U-BOATS. URGENCY REQUIRES INSTANT MEASURES. TEN MORE ARE TO SAIL FROM HERE NEXT WEEK."
"The dirty Boche!" added Cassidy. "Dugan has left for Mexico to look up this brother of his and I'm lookin' up this snake, so I guess there's no harm done so far."
"New York.
"January 3rd. 1916.
"My dear Brother: "For seven long weeks I have awaited a letter from you. The United-States mails from Mexico seem to be interrupted. Imagine my transports of joy when at last I hear from you today. You and I, dear brother, are the only ones left of our family--you in Vera Cruz. I in New-York--you in a hot Southern climate, I in a Northern, amid snow and ice, where the tardy sun does not route me from my bed till late in the morning.
"However, I inform you with pleasure that I am well. I rejoice that our good health is mutual. After all, the dear old U. S. suits me. Of course railroads or boats could carry me to a warm climate, in case urgency required it. But I am quite well now, and my health requires merely prudence. However, if I am again ill at any instant, I shall leave for Florida, where all tho proper measures can be taken to combat my rheumatism, "Ten days ago I was in bed, and unable to do more than move my left arm. But th« doctors are confident that my malady is not going to return. If it does threaten to return I shall sail for Jacksonville at once, and from there go to Miami, and not return here until the warm and balmy weather of next spring has lasted at least a week. Affectionataly your brother.
"Herman."
He pocketed the letter and went into the bedroom to get a coat and vest for the prisoner. Miss Erith looked at Vaux.
"Cassidy seems to know nothing about the code-cipher," she whispered. "I think he rummaged on general principles, not in search of any code-book."