A trail is not one smell. Men speak of it as though a dog simply smells a person and follows him the way you might follow a length of string laid along the ground, and it is not like that at all, or was not like that for me. Following a trail is more like listening to a single voice in a room full of people all talking at once, except the voices are smells, some shouting, some already nearly silent by the time you arrive. The sweetish scent was the shouting one that night. Under it, leather, new leather, boots not yet properly broken in. Under that, tobacco, though not Mr. Holmes's tobacco, something coarser. And under everything, so faint I nearly missed it, a smell I knew from the fish market by the river, brine and scale and the rot of a place where dead things are cut open every morning.
I went down the ivy on my own four legs rather than the climber's borrowed two, which I flatter myself was the easier journey, and found the trail again on the garden path below, running toward the back gate. Mr. Holmes and Dr. Watson followed with a lantern between them. I heard Mr. Holmes tell the young woman, Miss Ellery, that she must be patient, that a dog's work could not be hurried without ruining it. I thought this showed unusual good sense in a man. Most humans want you to run when running is the very thing that loses a trail entirely.
Before we ever reached the garden, though, there had been a good deal of talk in the front hall that I sat through, bored, while men in dark coats came and went. The household had suspected its own butler first, an old man named Craddock who smelled of nothing more sinister than snuff and boot polish, and I remember thinking, in whatever way a dog thinks such things, that they were wasting their evening on him. I had brushed past his legs twice on my way through the hall, and there was nothing on him worth following, nothing sharp or foreign or new, only the same steady smell he must have carried for thirty years of service in that house. A dog knows a man's ordinary smell the way he knows the ordinary creak of a familiar stair, and Craddock's had not changed at all. Mr. Holmes seemed to reach the same conclusion rather faster than the household had, and with considerably less ceremony, dismissing the butler from suspicion within a few minutes of arriving and turning his attention instead to the window latch, which I understand had been forced from the outside rather than opened from within.
"Your own people have been looking for treachery in the wrong direction," he told Miss Ellery's father, a stout, worried man who kept polishing his spectacles on his sleeve without ever quite getting them clean. "No servant did this. A servant would have used a key. Whoever came in tonight came in the hard way, and a man does not choose the hard way when the easy one is standing open to him, unless the easy one is barred to him for some reason of his own."
I did not understand a word of this at the time, of course, only the shape of the room easing, the worried man's shoulders coming down an inch, the way a house settles once the wrong question has finally stopped being asked in it.
We went out through the back gate and along a lane behind the square, and here the night did something unkind. It began to rain, not heavily, but the thin cold kind a human hardly notices and a dog feels as a small catastrophe, since it washes the top layer of a trail away almost as fast as it settles.
I nearly lost him here, in that lane, within the first quarter hour of the whole chase. This had never happened to me before, not with Small and his creosote, not with any lesser trail I had run in the years since. The sweetish scent thinned to almost nothing under the rain, and for perhaps thirty yards I had only the leather and the tobacco to work with, common enough smells that half the men in London could have laid them down that same evening for reasons that had nothing to do with any theft at all.
I stopped. A dog's shame is not so very different from a man's, I think, though we are better at hiding when it passes and worse at hiding when it starts.
Mr. Holmes crouched beside me again. "He's lost it," he said to Dr. Watson, not unkindly, more as a man reporting weather than passing judgment. "The rain has done what Small's creosote could never do to him three years ago."
"Can he pick it up again?" the doctor asked.
"That depends rather more on the dog than on either of us," Mr. Holmes said, and I have thought since that this was a kind thing to say. It put the whole burden back where it belonged, on four legs and a nose, and did not pretend that a man standing over me with a lantern could do the actual work for me no matter how clever he was.
I cast the lane in a widening circle rather than a straight line, since a straight line only finds a trail if you are lucky enough to already be standing on it, and a circle finds it eventually no matter where you began. It took longer than I would have liked. But near a drainpipe, where the overhang of a roof had kept a strip of pavement dry, I found the leather again, stronger, and beside it, faint but unmistakable, a thread of the sweetish scent the rain had not yet reached, caught in the lee of the wall the way smoke catches in the lee of a hill.