"And you are right," he snapped. "I admit I might not have got upon the right track had you not made that discovery. It was clever, Wigan." "It did not seem to help you to a theory," I answered. "True. But it made me ask myself a question. Had the thief found what he was looking for? Much depended upon the answer. If he had, I saw small chance of elucidating the mystery. I might have propounded a theory, but I should have had no facts to support it. "Indeed, had I theorized, then my theory would have been wrong. If the thief had not found what he wanted, he would continue his search, I argued. For some reason he connected Sir Joseph Maynard with the object of his search, and, when he tried again, we stood a chance of finding the link in the chain we wanted. It might implicate Sir Joseph, it might not. That is why I said we must wait. The thief has tried again--twice. Now, what is he looking for?" "Presumably something a doctor is likely to have," I said. "And not silver, nor money, nor papers, nor----" "Nor counters, I suppose," I interrupted. "Not precisely," said Quarles. "But those counters have inspired me. They crept into my brain, Wigan, and remained there. Whatever it is the thief is seeking for, he is desperately anxious to obtain it--witness his two attempts on consecutive nights." "You forget that days have elapsed since Sir Joseph's was broken into." "Forget? Nonsense!" said the professor sharply. "Should I be likely to forget so important a point? It means that opportunity has been lacking. More, it means that any doctor would not do, only certain medical practitioners. And that is where the counters help me--or I think they do." "How?" "Call for me to-morrow morning; we are going to pay a visit together. We may be too late, but I hope not. That revolver left in Dr. Wood's house rather frightens me." "Why, particularly?" "It proves that the thief will use violence if he is disturbed, and that he is a desperate man. I should say he will grow more dangerous with every failure." It was like Christopher Quarles to raise my curiosity, and then to leave it unsatisfied. It was his way of showing that he was my superior--at least, it always impressed me like this. No man has ever made me more angry than he has done. Yet I owe him much, and there is no gainsaying his marvelous deductions. He made me angry now, first by his refusal to tell me more, and then by his patronizing air when I left the house. "You are clever, Wigan, very clever. You have shown it in this case. But you lack imagination to step out as far as you ought to do. Cultivate imagination, and don't be too bound up by common sense. Common sense is merely the knowledge with which fools on the dead level are content. Imagination carries one to the hills, and shows something of that truth which lies behind what we call truth." I found him ready and waiting for me next morning, as eager to be on the trail as a dog in leash.