"A spy," I said. "Could it be anyone but Anderson?"

I decided to make inquiries when I got home; and instead of going to the club as was my wont in the evening, I hailed the first taxi I could find, and hurried back to my house. I took the precaution to examine the soil in the little garden before I left, and even brought a small piece away with me.

"Now if Anderson's out, and has any mud on his boots like this, I have him," I muttered. "And, vice versa, he has me to a certain extent; he must have seen me use the hypodermic."

If once he had any definite evidence against me, my life would not be worth living, and once he knew that I knew that he knew, my chances of beating him would become very much less. To-night should decide.

I reached home; he was out, but as no one had seen me go in, I left again secretly, and when I once more got back about midnight, there was Anderson sitting by the fire in felt slippers, smoking and drinking.

"What a beast of a night," he volunteered; it certainly was cold and damp. "I'm jolly glad I've been able to sit nice and quiet all the evening."