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.
His refusal to allow a doctor to see the Professor’s daughter was nothing short of culpable. Had Antonio, that sly, crafty Italian, to whom I had taken such instinctive dislike, summoned a doctor at once, it was quite possible that the poor girl’s life might have been saved.
But why had she returned to the house in a manner so secret? Why had she crept into the dining-room and removed her hat? It would almost seem as though she had returned for good, for if she had intended to go back to her aunt’s she would not have taken off her hat and laid it aside.
And why had she done so in the dining-room, of all places? Why had she not ascended to her own room? And why, most of all, had she not summoned Antonio?
Was it because of fear of him?
Kirk and Antonio were friends. That I had detected from the very first. The Italian was polite, urbane, servile, yet I saw that the bow was only a shallow make-believe. Alone together, the pair would, no doubt, stand upon an equal footing.
The reason she had returned home was mysterious enough, yet the greater problem was the reason why she also had been struck down and the same corrosive liquid flung into her fair countenance.
I could not think that Kirk was responsible for this second assassination, for, unless Antonio had lied, it had been committed at the very hour when I had been seated with my mysterious neighbour only a few doors away from my own house.
So, as you may readily imagine, I was still sorely troubled when at last the maid brought me my hot water and I rose to dress.
I quite saw now that the reason why Kirk had called to inspect the new Eckhardt tyre was merely in order to make my acquaintance. Yet it was certainly curious that he should have predicted the visits of the two other men for the same purpose. After breakfast I went, as usual, to the garage, but my mind was still full of the events of the previous night.
Kirk had arranged to call for me at eleven and return to Sussex Place, where he intended to search for any finger-marks left by the assassin. Eleven o’clock struck, but he did not arrive. In patience I waited until one, and then returned home to luncheon, as was my habit.
His non-arrival confirmed my suspicions. What, I wondered, could have been the purport of that mysterious message in German that he had listened to on the telephone just before we had parted?
At two o’clock I called at his house and rang the door-bell. There was no response. Both Kirk and his sister were out.
So I returned to the garage, and with Dick Drake, my stout, round-faced, dare-devil driver, who held two records at Brooklands, and was everlastingly being fined for exceeding the speed limit, I worked hard upon the refractory engine of a car which had been sent to me for repair.
All day it was misty, but towards evening the fog increased, until it became thick even in Chiswick, therefore I knew that it must be a regular “London particular” in the West End. One driver, indeed, who had come in from Romford, said he had taken four hours to cross London. Hence I resolved to possess my soul in patience and spend a quiet evening at home with my wife and her young sister, who lived with us.
Curiously enough, however, I found myself, towards six o’clock, again seized by a sudden and uncontrollable desire to return to Sussex Place in search of my mysterious neighbour. I felt within me a keen, irrepressible anxiety to fathom the curious problem which that shabby man, who declared himself immune from trial in a criminal court, had placed before me. Who could he be, that, like the King himself, he could not be brought before a judge?
At times I found myself laughing at his absurd statements, and regarding them as those of a lunatic; but at others I was bound to admit that his seriousness showed him to be in deadly earnest.
Well, to cut a long story short, at eight o’clock I took Dick Drake and managed to creep over in the fog to Regent’s Park on one of the small cars.
The door was opened, as before, by Antonio, who perceptibly started when he recognised me.
Yes, Mr Kirk was there, he admitted, and a few seconds later he came to me in the hall.
He was a changed man. His face was thinner, sallower, more haggard, and the lines about his mouth deeper and more marked; yet he greeted me affably, with many apologies for not keeping his appointment.
“I was here, very busy,” he explained. “I rang you up twice on the ’phone, but each time you were engaged.”
“Well,” I asked, going straight to the point, “what have you discovered?”
“Very little,” he said. “I’ve searched all day for finger-prints, but up to the present have found none, save those of Antonio, Ethelwynn, and members of the household.”
“You do not suspect any of the servants?” I whispered, full of suspicion of the crafty-looking Italian.
“Of course not, my dear sir. What motive could they have in killing such an excellent, easygoing master as the Professor?”
“Revenge for some fancied grievance,” I suggested.
But he only laughed my theory to scorn.
I followed him upstairs, through the red boudoir to the laboratory, to which the fog had penetrated, and there watched him making his test for recent finger-prints. His examination was both careful and methodical. He drew a pair of old grey suède gloves over his hands, and, taking up one after another of the bottles and glass apparatus, he lightly coated them with some finely powdered chalk of a grey-green colour, afterwards dusting it off.
On one or two of the bottles prints of fingers were revealed, and each of these he very carefully examined beneath the light, rejecting them one after the other.
To me, unacquainted as I was with the various lines of the finger-tips, all looked alike. But this shabby, mysterious neighbour of mine apparently read them with the utmost ease, as he would a book.
In its corner, in the same position in which we had left it on the previous night, lay the hideous body of the Professor, crouching just as