"You can't prove that!" cried Ellis, much excited.
"Only by deduction. Why should the man write in a cypher if his wife did not know the cypher?"
"The information, whatever it is, might have been intended for someone else."
"I don't think so. Moxton knew that his wife would be the first to discover his dead body, and wrote the message in cypher for her information. It is only reasonable to think so."
"Mrs. Moxton says she does not know what the cypher means."
"Precisely. She is telling lies and shielding the true criminal."
"How do you know that the cypher contains the name of the criminal, Harry?"
"Because I can read the cypher," was Cass's unexpected reply. "I found out the key yesterday. Look here, Bob." He jumped up from the sofa and, crossing to the writing-table, hastily scrawled two diagrams. "You see," he added, "here is a criss-cross, and a St. Andrew's cross with two letters in each angle which exhausts the alphabet."
Ellis looked at the diagrams with amazement and shook his head. "I am as much in the dark as ever. Explain."
"Well, you use the angles and the central criss-cross square for letters, with an added dot for the second letter. If you wish to write your name, 'Ellis,' in signs, you take the first letter of the third angle in the criss-cross, the two second letters of the sixth angle; the first letter of the square, and the first letter first angle St. Andrew's cross."