"Since experts may at times make mistakes, I grant that my negative evidence is not as convincing as it might be," said Quarles, "but I want the point conceded. I want, as it were, a base line upon which to build my theoretical plan. I want to forget the burglaries, in fact, and come to the Clarence Lodge case by itself. So we have a dead man and we first ask who shot him. Crosland says he did, and tells us the circumstances, his sister confirms his statement, and the butler, the woman servant and the nurse, who are quickly upon the stage in this tragedy, see no reason to disbelieve the statement. We burrow a little deeper into the evidence, and we discover one or two interesting facts. The man was shot on the left side of the head, a clean wound above the left ear. Crosland says he fired after he had been fired at, so the man, directly he had fired, must deliberately have turned his head to the right, which at least is remarkable. Further, to hit the wall of the landing in the place he did the man must have stood in the very center of the stairs to fire. His body was found some feet away from this central position, and a bullet so fired and striking where it did could not have missed two people standing on that landing. I have made a rough plan here," and Quarles took up the papers from the table, "giving the position of the dead man, the position of the walls and stairs. The lines show where the bullet would have hit if fired from a spot nearer where the dead man was found." I examined his diagram closely. "A man shot through the brain might fall several feet away from where he was standing," I said. "Yes, behind where he was standing, or perhaps forward, but hardly to one side. However, we burrow again, and we try and answer Zena's question why it was Helen Crosland who ran for the police. Why not? we may ask. Her close association with her brother in the affair, her anxiety on his account, make it natural that she should dash out not only for help but to make it certain that they had nothing to hide. Her words to Poulton, 'The burglars, and I am afraid my brother has shot one of them,' are significant. They tell the whole story in a nutshell. Crosland's statement merely elaborates it, over-elaborates it, in fact. The bolts on the front door, Wigan, were very stiff; I tried them. Helen Crosland would certainly have had difficulty in drawing them back, and it is an absurdity for her brother to declare that she had gone before he knew what she was doing." I had no comment to make, and Zena leaned forward in her chair, evidently excited. "It is a point to remember that she ran out exactly at the moment Poulton was passing, which may have been chance, of course, but from that room over the hall one can see down the drive and, by the light of a street lamp, some way down the road. Had any one watched there he could have prompted the girl when to start."