"You ask him these two questions and get him to answer definitely," said Quarles in that aggravating and dictatorial manner he sometimes has. "To-morrow night come to Chelsea. I am not prepared to talk any more about the Tavener case until then." Without another word he went off in the direction of Victoria, leaving an angry man behind him. I am afraid I swore. However, I hunted up the driver of the taxi, and went to Chelsea the following night, still somewhat out of temper. Quarles and Zena were already in the empty room waiting for me. "Well, what did the man say?" asked the professor. "The fog did not stop him anywhere until he got to Hyde Park Corner, and he is sure Lady Tavener was alone after leaving Richmond." "He stuck to that?" "He did, but after some consideration he said that he had almost come to a standstill in Hammersmith Broadway on account of the trams. I suggested that some one might have got into the taxi then, but while admitting the bare possibility, he did not think it likely." "Did he give you the impression that he believed Tavener guilty?" "Yes. He seemed to consider his arrest a proof of it." "Naturally," said the professor. "Your whole investigation seems to be for the purpose of proving Sir John innocent," I said. "Why were you so anxious to have him arrested?" "Pardon me, my one idea is to get at the truth. Always be careful of your premises, Wigan. That is the first essential for a logical conclusion. Zena has said that because a dog has a bad name I want to hang him. Well, she gave me an idea; started a theory, in fact. Let us go through the case. First there is the question of suicide. It must come first, because if we are logical--the law is not always logical, you know--if we are logical, it is obvious no man could be hanged while the doctors stuck tight to their opinion. However, I have reason for leaving the question of suicide until last. Therefore we investigate the question of murder. Had Sir John disappeared after visiting the house on Richmond Green, I suppose not one person in ten thousand would have believed him innocent." "But he didn't," I said. "No," said Quarles. "But he behaved in a most peculiar manner. He left immediately after dinner, did not reach home until after midnight, and has not yet attempted to account for his time. He was in an abnormal condition. We will make a mental note of that, Wigan." I nodded.