"She told you that you were a spy—that I had used you as a tool," he said sharply. "You have been hurt by her words. I don't want you to feel that you are anything but a free agent, or to do anything that you consider dishonourable. But I must know whether you are still willing to act with us, or whether you wish to stand aside."

Fairfield threw the stump of cigarette viciously into the fire.

"I am acting with you, of course," he answered

sullenly, "though I wish you to ask for my help only when it is absolutely necessary. What I complain of is, that I have not been frankly treated, and that I have been placed in an invidious position with Lady Eileen. You must remember that I have feelings, and that it is not pleasant to be told one is acting as a spy, especially by—by an old friend. You know, Mr. Foyle, that I have only been wishful to serve those I have known."

There was something pathetic in his endeavour to justify his actions to himself. Foyle murmured a sympathetic, "I understand—yes, yes, I know," and then became thoughtful.

"After all," he said at last, "this does not make us so very badly off. You are openly on our side now, Sir Ralph, so there can be no fear of your again being accused of acting in an underhand manner. There is nothing more to be done at the moment. I will keep you posted as to any steps we are taking."

"Very well. Good morning, Mr. Foyle."

The baronet was gone. The superintendent resumed his perusal of documents. He felt some little compunction at what had happened. Yet it was his business to clear up the mystery, and to use what instruments came to his hand, so long as the law was not violated. There is a code of etiquette in detective work in which the first and most important rule is: "Take advantage of every chance of bringing a criminal to justice." In using Fairfield as an instrument, Foyle was merely following that code.

In a little, Foyle had finished and sent for Green. The chief inspector came with a report.