He was no doubt correct. Even I was capable of making these deductions. But I still did not understand how the time of death would help us uncover the identity of the murderer.
But the detective was far from finished.
“The water is rather warm,” he said, swishing his fingers in the canal. “Its corridor is wide and most of the day the sun shines on it.”
“My theory,” he continued, drying his fingers on his coat, “is that the body floated here from one of the tributaries, which are narrow and shady. And those winding streets around them practically invite wrongdoing.”
I glanced around both sides of the canal, which was one of the main city communications, and which after several hundred yards flowed into the Grand Canal.
“But there are dozens of these side streams!”
“Use your brain, my friend! I know that I pulled you out of bed at an ungodly hour, but even in this condition you are capable of deducing this basic physical fact!”
“Currents!” I cried. “All we have to do is figure out where they go and they will lead us to the site of the murder!”
“You see, you are not so poorly off after all,” said the detective, slapping me on the shoulder. “But that is not all. At such a busy hour Paolo would not float along the surface more than a few minutes without being discovered. I think we ought to head to the closest stream against the current, which is this one.”
He was pointing at a rivulet on the other side of the canal. We crossed the arched bridge and headed towards it.
It was a typical Venetian rivulet, just a few yards wide, hardly big enough for a craft to pass through, and with a humble walkway running alongside it. On both sides rose the flaking walls of a palace, above which shone the first rays of the morning sun.
For the first time I felt just how confined the city really was. We could not even walk side by side and we had to proceed in single file. Venice suddenly began to feel rotten, as though something distasteful and corrupted were lurking behind the romantic facade and glistening surface of the Grand Canal.
After a few hundred yards the rivulet forked, merging into two other canals, along which the walkway was even narrower. Laundry hung on lines between the houses: shirts, stockings, trousers and striped gondoliers´ leotards. Above the water rose a strange haze; everything suggested that visitors were unwelcome.
“Where to now?”
“Each of us will take one side. If either of us comes across anything suspicious we will signal the other.”
Without waiting for me to reply he plunged into the morning gloom of the street on his right.
I never would have told him that I was afraid, but I humbly admit to you, dear reader, that I was terrified. As his footsteps grew more distant a shiver went down my spine. I was alone against a narrow and twisting wall, the air smelled of sewerage, and just a few hours earlier our friend had lost his life somewhere here. I would not be surprised were some rogue to take mine as well. I could only hope that the criminals were still fast asleep in their beds.
I started off on the opposite side from where Holmes had disappeared and carefully stepped along the cobblestones. Behind the closed windows above me Venice started to awaken. Coffee was brewing, kettles were whistling, toilets were flushing.
All of these sounds terrified me and distracted me from what the detective had asked me to do. If a letter from the murderer with an exact description of how he had killed Paolo were lying in plain view, I surely would not have noticed it.
I had already gone quite a ways from the crossroads where we had separated when from a distance I heard Holmes calling.
Exhaling with the relief of not having to continue along the dark and unfriendly street, I ran back. A few yards after the confluence of the canal I found the detective kneeling at the edge of the bank and staring at the water.
“What did you find?”
“A stain,” he said.
Indeed, on the surface of the water together with other waste floated an odd greasy stain. It was slowly dissolving in the water, but more grease flowed from the ducts protruding into the canal from grooves in the pavement. Perhaps it came from the drainage of one of the restaurants.
“You surely must have noticed that Paolo’s clothes were greasy. It is likely that the water carried him from here.”
I looked in the direction in which he pointed. Nearby the current flowed into another, wider canal.
“Our friend drowned somewhere between this spot and the start of the street. If we thoroughly search the pavement and the banks we will no doubt find clues.”
Like a bloodhound that has found the trail, the detective began scanning the ground yard by yard. The morning light was gaining in intensity and it was only a matter of ten or twenty minutes before people would begin to appear and the water would be filled with rowboats and gondolas.
I also searched, though I did not know precisely for what. Holmes fortunately was not counting on me.
“Eureka!” he cried presently, picking up from the ground a cobblestone lying haphazardly in a puddle under a gutter. “If I am not mistaken this is the murder weapon! The edge of the stone corresponds to the size of the wound in Paolo’s skull and confirms my theory that the killer used the first thing he could find.”
Upon closer examination of the stone we found dark and smudgy stains resembling human blood.
“You see, it is not difficult to calculate the exact time of death when we measure the speed of the current of all the canals through which the body floated and consider the distance which it travelled. I do not think that it will differ much from my estimate.”
“We now know where and how the murder occurred,” I said, “but I still do not understand how it will get us closer to the murderer. The water washed off the fingerprints and it is hardly likely we will find any witnesses.”
“The time has come for real detective work!” said Holmes, removing from his pocket his indispensable magnifying glass. He bent over the pavement and despite his rheumatism paced quickly back and forth with his nose just an inch from the surface.
The bulldog persistence with which he had apprehended so many criminals was again in evidence.
“You see how the mildew on the curb is scraped off here, whereas elsewhere there is an unbroken mossy growth?” he pointed out. “This is where the killer dragged the unconscious Paolo to the water and threw him in.”
The detective knelt on the damp cobblestones and examined the spot more closely. A short distance from us the doors of a house opened and a worker emerged. Unfortunately he was headed towards the spot that my companion was currently examining.
“Make certain nobody walks here!” Holmes barked. “I only need a few more minutes!”
I stopped the sleepy man and asked him to take a different route, hoping against hope that no one else would come. I did not want to get into a skirmish with a gondolier’s fists.
Another whoop from the detective allayed my fears. He put away the magnifying glass and between the place where we found the rock and where Paolo’s body had been thrown into the water he used his pocket knife to pick up a cobblestone and proudly showed me the soil sticking to it.
“This soil is the answer to our entire investigation,” he explained to me, as clearly I was unable to follow the trail of his logical deductions. “You will not find this soil in all of Venice. The local soil is coarse and dark with a large proportion of sand. But the soil that I am holding in my hand was brought here on the shoes of the murderer, probably a size five.”