“My word, Hargrave,” he said, “old Arnold is a clever beggar! He cleared the thing up clean as rain.” The Baronet spread the newspapers out before him.
“We knew here at the Criminal Investigation Department that this thing was a cipher of some sort, because we knew about these horses. We had caught up with this business of importing horses. We knew the shipment was on the way as I explained to you. But we didn't know the port that it would come into.”
“Well,” said the American, “did you find out?”
“My word,” he cried, “old Arnold laughed in my face. 'Ach, monsieur,' he cried, mixing up several languages, 'it is Heidel's cipher! It is explained in the seventeenth Criminal Archive at Gratz. Attend and I will explain it, monsieur. It is always written in two paragraphs. The first paragraph contains the secret message, and the second paragraph contains the key to it. Voila! This message is in two paragraphs:
“'"P.L.A. shipped nine hundred horses on freight steamer Don Carlos from N. Y.
“'"Have the bill of lading handed over to our agent to check up.”
“'The hidden message is made up of certain words and capital letters contained in the first paragraph, while the presence of the letter t in the second paragraph indicates the words or capital letters that count in the first. One has only to note the numerical position of the letter t in the second paragraph in order to know what capital letter or word counts in the first paragraph.'”
The Baronet took out a pencil and underscored the words in the second paragraph of the printed cipher: “Have the bill of lading handed over to our agent to check up.”
“You will observe that the second, the eighth and the eleventh words in this paragraph begin with the letter t. Therefore, the second, the eighth and the eleventh capital letters or words in the first paragraph make up the hidden message.”
And again with his pencil he underscored the letters of the first paragraph of the cipher: “P.L.A. shipped nine hundred horses on freight steamer Don Carlos from N. Y.”