"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."
"I see, and 'L' being the second letter of the sixth angle you put a dot."
"Of course. If I wrote 'K' I should put no dot," replied Harry, and took a morsel of paper out of his pocket. "Here," said he, "is a copy of the sign on the dead man's arm. The second letter of ninth angle criss-cross: the first letter second angle St. Andrew's cross, and the second letter fourth angle of the same. Do you see? Now take this pencil, Bob, and use the key to turn them into letters."
Ellis did so, and produced three letters on the paper given to him. "'R U Z,'" he read slowly. "What does that mean? Is it a word?"
"I don't think so. There is no word spelt 'Ruz' in any language that I am acquainted with. I believe those three letters are the initials of the man who killed Moxton. For some reason the dying man did not desire to give up his murderer to justice, but at the same time he wished to let his wife know who struck the blow, hence the cypher. Mrs. Moxton can read the meaning, depend upon it, Bob."
"It seems strange," assented Ellis, surveying the letters thoughtfully. "Do you think there are three names here, or only two?"
"I can't say. 'R U' may mean Rupert or Rudolph, but I am in the dark so far. I have discovered the letters, Bob; it is for Mrs. Moxton to explain them to you."