hands all cipher advertisements for the personal column. If the
advertisement came through the post, their time would be thrown away. If
it was delivered by hand, there was a chance of learning whence it had
been dispatched. The intervention of Lady Eileen was an accident that
could not have been foreseen. In that matter luck had played into
Foyle's hands.

CHAPTER XXX

Between Berkeley Square and Scotland Yard, Fairfield consumed ten
cigarettes in sharp jerky puffs. Yet he was scarcely conscious of
lighting one. Indeed, as he climbed the wide flight of steps at the main
entrance, it seemed as though no palpable interval of time had elapsed
since he had been practically turned out of her father's house by Eileen
Meredith.

Heldon Foyle put away the bundle of documents that contained the history
of the case as the baronet was announced, and waved his visitor to a
chair.

"Well?" he asked.

Fairfield shrugged his shoulders. "A nice mess you've got me into," he
complained. "Why didn't you tell me you knew the secret of the cipher?"

The detective's face was full of ingenuous surprise as he answered--

"Didn't I? I thought I made it perfectly clear to you. I am sorry that
you misunderstood. I should have made it plainer. What has gone wrong?"

Sir Ralph made an impatient gesture. "Oh, what's the use of talking
nonsense? You did not tell me that you knew the cipher, and as a
consequence Lady Eileen now knows that you know."

The superintendent gave no indication of the chagrin with which the news
filled him. His features were perfectly expressionless. A part of his
plans had failed from excess of caution. He did not need Fairfield to
tell him what had happened. He could make a fairly accurate guess as to
the manner in which he had been unwittingly betrayed. His thoughts
turned at once to the question of what the girl would do. If he had
judged her right, she would try to warn Grell. Either she knew his
address or not, but it was unlikely that she did, as they were
communicating in cipher. The obvious thing for her to do was to try to
stop the advertisement. There was, however, little he could do. He had
men on duty in Berkeley Square and in Fleet Street. He would soon hear
of any new developments.

"That's a pity," he said reflectively. "It may mean a re-arrangement of
our plans. And believe me, Sir Ralph, I badly regret now that I did not
go into fuller details with you. What happened?"

Stumblingly, S