"I know it was murder," returned the professor sharply, "and the manner of it has presented the chief difficulty I have found in demolishing my theory altogether. Bridwell was poisoned by an injection. The hypodermic needle was inserted under the hair at the back of the head, here in the soft part of the base of the skull, the hair concealing the small mark it made. I believe the secret of the poison used is forgotten, but you may read of it in books relating to the Vatican of old days and concerning the old families of Italy. I might mention the Borgias particularly. So you see my difficulty, Wigan. The crime literally reeked of Italy, and we had two Italians amongst our dramatis personæ."
"A significant fact," I said.
"Of course I am letting the doctor know of my discovery; that is the good turn I shall do him. He will be considered quite smart over this affair. Now consider this point. It would surely have been very difficult, once the host's suspicions had been aroused, to make the injection without a struggle on the victim's part."
"No suspicion may have been aroused," I said. "Masini has told us of a map. The murderer might have been leaning over his victim examining it."
"That is true. You pick out the weak point," said Quarles.
"Even then there would have been some sort of struggle, surely," said
Zena. "The poison can hardly act instantaneously."
"Practically it does," Quarles answered. "I have read of it, of the different methods of its administration, and of its results, and no doubt any one acquainted with old Italian manuscripts would be able to get more detailed information than I have; but it produces almost instant paralysis, acts on the nerve centers, and stops the heart's action, leaving no trace behind it. What straggle there was could be overcome by the pressure of a man's hand upon the victim's chest, to keep him from rising from his seat, for instance. I found signs of such a detaining hand on Bridwell's shirt front. Of course, Wigan, while pulling my theory to pieces I knew nothing of your facts about Bridwell, but now that I do know them, the theory is not saved from ruin. Have you ever watched trains rushing through a great junction—say Clapham Junction?"
"Yes; often."
"And haven't you noticed how the lines, crossing and recrossing one another, seem to be alive, seem to be trying to draw the train to run upon them, to deviate it from its course, until you almost wonder whether the train will be able to keep its right road? There seems to be great confusion; yet we know this is not so. We know those many lines are mathematically correct. If you want to keep your eye on the main line, you mustn't be misled by the lines which touch and cross it, which seem to belong to it, until they suddenly sweep off in another direction. In this Bridwell affair we have to be careful not to be misled by cross lines, and I grant there are many. You say the woman is an extraneous episode; but is she? She left a bag, which is not to be found. Had Masini known of her existence I do not think he would have denied all knowledge of her, for the reasons I have already given, and I argue that her visit to the flat was timed to occur when the servant was out, so that he should know nothing about her. The hall porter knew nothing; about a lady visiting the flat at any time, so we must assume the woman was not a constant visitor. Moreover, we know that she had something to hide, some secret, or she would not have ceased speaking directly she found she was addressing a stranger. She probably belonged to Bridwell's private life. Now Zena says, 'Cherchez la femme,' but there is no need to look for her; she forces herself upon our notice. We know that Bridwell was alive at seven o'clock: we know his visitors did not leave him until eight. It is hardly conceivable that the woman came to the flat after that to commit a crime, impossible to believe that she would leave her bag there to be evidence against her, and then telephone about it to a man she knew to be dead. We may dismiss from our minds any idea that she committed murder."
"I can see a possibility of immense subtlety on her part," I said.