I don't believe him to be
a murderer, but why does he remain in hiding? He is not the sort of man
to do foolish things, and that is foolish on the face of it. He has some
strong reason for being out of the way. Can you explain?"

She pulled her chair closer to him, and laid one slim hand on his.

"I cannot explain--I can only trust. He looked to us to help him. I know
that he wants money, for he sent a friend to tell me. I had none, but I
gave her my jewels. Detectives were watching her, and they, with the
connivance of my father, took them from her. Now, you, his most intimate
friend, must help him. He has given you the key to the cipher which will
appear, and then, I suppose, he will tell you how to get it to him."

She had apparently taken it for granted that the baronet was with her in
whole-souled devotion to her lover. His fingers beat a tattoo on his
knee.

"So that advertisement was the key to a cipher? Do you know when I shall
get a message?"

"I shall get one to-morrow. You--who knows?"

"Then you can tell me how to read it?"

She hesitated a moment, finger on chin. Then, animated by a quick
resolve, she moved to a little inlaid desk and unlocked a drawer. She
returned with a piece of paper in her hand.

"What was the number mentioned in your advertisement?"

"2315."

For a little the only sound in the room was the scratching of pencil on
paper. At last she finished, and handed the result to him. He wrinkled
his brows as he studied it.

THIS IS THE KEY
2315 23 152 315
VKJX KV UMG NFD

"The bottom line is the top one turned into cipher," she explained. "The
middle line is the key number. In the first word you take the second
letter from T, the third from H, the first from I, and so on. It is a
cipher that cannot be unravelled without the key number. H becomes K
once and M once."

"I see." The simplicity of it at once dawned on him. "That was what
Foyle meant when he said that some ciphers could not be solved by the
recurring E," he said unthinkingly.

She had risen and flung away from him in quick revulsion. One glance at
her face told him what he had done.

"You spy!" There was stinging scorn in her tone. "You have talked it
over with Foyle, and that man knows all. You are here to worm out what I
know in order to betray your friend. Oh, don't trouble to lie,"--as he
would have spoken,--"I can see your object. And I nearly fell into the
trap."

The man was not without dignity, as he stood