"Track!" said my master. Like any obedient tracker-dog who has received the command he most loves, I gave a bark of excitement, put my nose down to the ground and sniffed. A small group of people gathered behind us. Among these onlookers was the old caretaker of the building next door to ours. He spoke in a scornful voice, "You actually think your dog might catch a thief three days after the event?" My master said nothing, but I'm sure he must have smiled. I did not turn to look. I knew he would not speak unless it was to give me a new command. I needed to concentrate. My task was difficult. I had to pick out one scent among the many that lay about and then tracked it to its source. "I've seen many tracker-dogs in my time," said the caretaker to the onlookers. "I served with the police years ago. We would never have thought of using a tracker-dog to find a car thief. Impossible. Everyone knows that dogs are useless in such matters."He ’ s got his car back, so what ’ s the use of parking it again in the same place and trying to pick up one scent among the hundreds on this pavement? It ’ s like asking the dog to do a crossword puzzle! ” In a sense he was right. I'm sure there's no need to tell you that, just as a dog's hearing is much better than a human being's, so his sense of smell distinguishes one thing from another far better than the most powerful magnifying glass in the world. If Sherlock Holmes could work out that a man had had an egg for breakfast by seeing the yellow stain on his mouth, a trained dog could tell you whether the hen that laid the egg was healthy or not. I know it sounds funny and I mean it to be. But I'm not exaggerating. A dog can tell you-provided you understand a dog's way of communicating-all this and more without even setting eyes on the man he is investigating. But here the ground was criss-crossed in a complex knot of different smells and scents and tracks. To untie it and follow one of them, seemed like asking for a miracle.