Fairfield came to an abrupt halt and gripped his companion by the arm.
"You intended— For what reason? How could you know?"
"Absolute common sense, my dear sir. That's all. Absolute common sense. If you are a chess-player, you know that the man who can foretell what move his opponent is going to make usually wins. Here, let's find a quiet Piccadilly tea-shop and I'll tell you all about it."
There is no place which one may find more convenient for a quiet conversation than the London tea-shop before twelve in the morning. Over a cup of coffee in the deserted smoking-room Foyle spoke to the point.
"I did not tell you why I took you to see Lady Eileen, because I was afraid you might refuse. She has been antagonistic to you hitherto. The fact that Grell advertised you in somewhat the same manner as herself has given her the idea that, after all, you too might be trying to shield him. Naturally, she wants to be certain, in order that you may join forces. That's why I prevented you saying anything. Now, if you go back to her you may tell her that I practically forced you to accompany me. You can win her confidence, and through her we may get on the right track."
An angry flush mounted to Fairfield's temples.
"In short," he said curtly, "you want me to act as a spy on an unsuspecting girl. No, thanks. That's not in our bargain."
He was genuinely angry at the proposal. The superintendent saw that he had been too blunt, and made haste to repair his error.
"Don't be in a hurry," he protested. "The girl, as I told her, is beginning to be mixed up in a dangerous business. This is the only way to extricate her.