What had been told him over the telephone had caused an entire change in his manner. Previously he had been dictatorial and defiant. He was now cringing, crushed, terror-stricken.
The grim scenes I had witnessed surged through my brain. The mystery of it all had gripped my senses. Carefully I analysed each event, trying to discern some light as to its cause and motive. But I was not a professional detective. This was the first time I had found myself mixed up in a crime by which human life had been lost.
That the death of Professor Greer was no ordinary crime of violence I had quickly recognised. There was some subtle motive both in the crime itself and in the supposed presence of the Professor in Edinburgh, whereas in reality he was already lying dead in his own laboratory.
Those instructions to his daughter, which seemed to have been written after his departure from King’s Cross, also formed an enigma in themselves. The dead man had actually sought the assistance of his worst enemy!
Yet, when I weighed the circumstances as a whole calmly and coolly, I saw that if the unknown person to whom the Professor had signalled on that fateful night could be found a very great point would be gained towards the solution of the problem.
The pulling up and down of the drawing-room blind was, no doubt, in order to inform some person waiting without of his journey north. Was that person who received the signal afterwards the assassin?
Yet the fact that the crime was committed behind locked doors, that both the victim and the assassin had to pass within a few feet of where Miss Ethelwynn was seated, and that into the unfortunate Professor’s face some terribly corrosive fluid had been dashed, formed a problem which held me mystified.
There was something uncanny in the whole inexplicable affair. I now realised for the first time how complete was the mystery of the Professor’s death, even apart from the other facts of his signals and his journey north.
Kirk, this dealer in secrets, admittedly posed as a friend of the family. Greer trusted him. To him Ethelwynn had fled for assistance at the first suspicion of anything being wrong. Therefore would it not have been easier for him than for anyone else to enter the house in secret and kill the man who had stolen from him that mysterious secret?
Yet, try how I would, I was unable to rid myself of the grave conviction that my new acquaintance was cognisant of more than he had told me. He was naturally a reserved man, it was true; yet there was an air of cosmopolitanism about him which spoke mutely of the adventurer.