I groaned. I had forgotten the problem of the shot in the dark. Assuredly it was a poser, for the feat was well-nigh impossible, unless we explained it by assuming a previous shot, which would have been all to the good if McKelvie could only have found the lost bullet.
"You have reverted to the theory that the crime was one of impulse," continued McKelvie. "Disabuse your mind of any such idea. That murder was premeditated. It was done in cold-blood, and planned down to the smallest detail, days before it occurred. And so very carefully was it planned that the criminal was able to work Mrs. Darwin into the scheme, without in the least disturbing his previous calculations. That is why we are stumped for the present, because I have not yet been able to put my finger on the weak spot in the link. There is bound to be a weak spot, there always is no matter how clever the criminal, but it may take longer than the time at our disposal before the trial. I shall have to pick up a new trail, since Orton had nothing of value to give us," McKelvie ended, knocking the ashes from his pipe. "Speed her up a little, Mr. Davies."
"What new trail?" I asked, obeying mechanically.
"The woman in the case," he said impressively.
"The woman in the case? You mean—Cora Manning?" I inquired.
"Yes. You know the old French saying, 'Cherchez la femme.' I have done my best to keep my promise to Mrs. Darwin to let Miss Manning out of it, but now it is a matter of necessity. I firmly believe she was in Darwin's study that night, somewhere between eleven-thirty and midnight," he answered.
"But, heavens, man, how did she get in?" I cried.
"She lodges, or did, at Gramercy Park. Drive me over there. She should be back by now and if she should prove to be the woman in the case, we'll make her talk. It ought not to take more than an hour at most, and if I am wrong, why we shall be no worse off than we are now."
I gave my car more gas and continued down Broadway, intending to cut across Twenty-first Street to Gramercy Park, remarking as I did so, "You haven't told me how she effected an entrance into that closed room."
"She must have entered by the secret entrance," he replied. "Eliminate the impossible, you know."