One of the little twigs which had crept in between the planks was broken, and it had been broken very recently, for the leaves were still fresh and the sap was oozing from the crushed stem. Muller walked over to the fence and examined the twig carefully. He soon saw how it came to be broken. The broken part was about the height of a man's knee from the ground. And just at this height there was quite a space between two of the planks of the fence, heavy planks which were laid cross-ways and nailed to thick posts. It would have been very easy for anybody to get a foothold in this open space between the planks.

It was very evidently some foot thrust in between the planks which had broken the little willow twig, and its soft rind had left a green mark on the lower plank. "I wonder if that has anything to do with the murder," thought Muller, looking over the fence into the lot on the other side.

This neighbouring plot was evidently a neglected garden. It had once worn an aristocratic air, with stone statues and artistic arrangement of flower beds and shrubs. It was still attractive even in its neglected condition. Beyond it, through the foliage of its heavy trees, glass windows caught the sunlight. Muller remembered that there was a handsome old house in this direction, a house with a mansard roof and wide-reaching wings. He did not now know to whom this handsome old house belonged, a house that must have been built in the time of Maria Theresa,... but he was sure of one thing, and that was that he would soon find out to whom it belonged. At present it was the garden which interested him, and he was anxious to see where it ended. A few moments' further inspection showed him what he wanted to know. The garden extended to the beginning of the park-like grounds which surrounded the old house with the mansard roof. A tall iron railing separated the garden from the park, but this railing did not extend down as far as the quiet lane. Where it ended there was a light, well-built wooden fence. Along the street side of the fence there was a high thick hedge. Muller walked along this hedge until he came to a little gate. Then crossing the street, he saw that the house whose windows glistened in the sunlight was a house which he knew well from its other side, its front facade.

Now he went back to the elder tree and then walked slowly away from this to the spot where he found the broken willow twig. He examined every foot of the ground, but there was nothing to be seen that was of any interest to him—not a footprint, or anything to prove that some one else had passed that way a short time before. And yet it would have been impossible to pass that way without leaving some trace, for the ground was cut up in all directions by mole hills.

Next the detective scrutinised as much of the surroundings as would come into immediate connection with the spot where the corpse had been found. There was nothing to be seen there either, and Muller was obliged to acknowledge that he had discovered nothing that would lead to an understanding of the crime, unless, indeed, the broken willow twig should prove to be a clue. He sprang back across the ditch, turned up the edges of his trousers where they had been moistened by the dew and walked slowly along the dusty street. He was no longer alone in the lane. An old man, accompanied by a large dog, came out from one of the new houses and walked towards the detective, he was very evidently going in the direction of the elder-tree, which had already been such a centre of interest that morning. When he met Muller, the old man halted, touched his cap and asked in a confidential tone: "I suppose you've been to see the place already?"

"Which place?" was Muller's reserved answer.

"Why, I mean the place where they found the man who was murdered. They found him under that elder-tree. My wife just heard of it and told me. I suppose everybody round here will know it soon."

"Was there a man murdered here?" asked Muller, as if surprised by the news.

"Yes, he was shot last night. Only I don't understand why I didn't hear the shot. I couldn't sleep a wink all night for the pain in my bones."

"You live near here, then?"

"Yes, I live in No.1. Didn't you see me coming out?"

"I didn't notice it. I came across the wet meadows and I stooped to turn up my trousers so that they wouldn't get dusty—it must have been then you came out."

"Why, then you must have been right near the place I was talking about. Do you see that elder tree there? It's the only one in the street, and the girl who brings the milk found the man under it. The police have been here already and have taken him away. They discovered him about six o'clock and now it's just seven."

"And you hadn't any suspicion that this dreadful thing was happening so near you?" asked the detective casually.

"I didn't know a thing, sir, not a thing. There couldn't have been a fight or I would have heard it. But I don't know why I didn't hear the shot."

"Why, then you must have been asleep after all, in spite of your pain," said Muller with a smile, as he walked along beside the man back to the place from which he had just come.

The old man shook his head. "No, I tell you I didn't close an eye all night. I went to bed at half-past nine and I smoked two pipes before I put out the light, and then I heard every hour strike all night long and it wasn't until nearly five o'clock, when it was almost dawn, that I dozed off a bit."

"Then it is astonishing that you didn't hear anything!"

"Sure it's astonishing! But it's still more astonishing that my dog Sultan didn't hear anything. Sultan is a famous watchdog, I'd have you know. He'll growl if anybody passes through the street after dark, and I don't see why he didn't notice what was going on over there last night. If a man's attacked, he generally calls for help; it's a queer business all right."

"Well, Sultan, why didn't you make a noise?" asked Muller, patting the dog's broad head. Sultan growled and walked on indifferently, after he had shaken off the strange hand.

"He must have slept more soundly than usual. He went off into the country with me yesterday. We had an errand to do there and on the way back we stopped in for a drink. Sultan takes a drop or two himself occasionally, and that usually makes him sleep. I had hard work to bring him home. We got here just a few minutes before half-past nine and I tell you we were both good and tired."

By this time they had come to the elder-tree and the old man's stream of talk ceased as he stood before the spot where the mysterious crime had occurred. He looked down thoughtfully at the grass, now trampled by many feet. "Who could have done it?" he murmured finally, with a sigh that expressed his pity for the victim.

"Hietzing is known to be one of the safest spots in Vienna," remarked Muller.

"Indeed it is, sir; indeed it is. As it would well have to be with the royal castles right here in the neighbourhood! Indeed it would have to be safe with the Court coming here all the time."

"Why, yes, you see more police here than anywhere else in the city."

"Yes, they're always sticking their nose in where they're not necessary," remarked the old man, not realising to whom he was speaking. "They fuss about everything you do or don't do, and yet a man can be shot down right under our very noses here and the police can't help it."

"But, my dear sir, it isn't always possible for the police to prevent a criminal carrying out his evil intention," said Muller good-naturedly.

"Well, why not? if they watch out sharp enough?"

"The police watch out sharper than most people think. But they can't catch a man until he has committed his crime, can they?"

"No, I suppose not," said the old man, with another glance at the elder-tree. He bowed to Muller and turned and walked away.

Muller followed him slowly, very much pleased with this meeting, for it had given him a new clue. There was no reason to doubt the old man's story.