He fished it out of his inside pocket and spread it on the dining
table under the light.

"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