Mule detects channis

"Then I'll explain. Only one kind of man can both know the location of the Second Foundation and prevent me from learning it. Channis, I'm afraid you're a Second Foundationer yourself."

And Channis' elbows rested on his knees as he leaned forward, and through stiff and angry lips said: "What is your direct evidence? Deduction has proven wrong twice today."

"There is direct evidence, too, Channis. It was easy enough. I told you that my men had been tampered with. The tamperer must have been, obviously, someone who was a) Unconverted, and b) fairly close to the center of things. The field was large but not entirely unlimited. You were too successful, Channis. People liked you too much. You got along too well. I wondered-

"And then I summoned you to take over this expedition and it didn't set you back. I watched your emotions. It didn't bother you. You overplayed the confidence there, Channis. No man of real competence could have avoided a dash of uncertainty at a job like that. Since your mind did avoid it, it was either a foolish one or a controlled one.

It was easy to test the alternatives. I seized your mind at a moment of relaxation and filled it with grief for an instant and then removed it. You were angry afterwards with such accomplished art that I could have sworn it was a natural reaction, but for that which went first. For when I wrenched at your emotions, for just one instant, for one tiny instant before you could catch yourself, your mind resisted. It was all I needed to know.

"No one could have resisted me, even for that tiny instant, without control similar to mine."

Channis' voice was low and bitter: "Well, then? Now what?"

Chapter 5