Then he slowly walked out into the middle of the street, paused, stared about him. A motorist paused to hurl some sarcastic comment. Another driver applied the brakes with sufficient force to skid the tires. But Sidney Zoom seemed entirely oblivious of them. He was engaged in looking up and down the street, carefully scanning the buildings upon either side.

  At length he crossed to the opposite side, walked down the sidewalk for some fifty yards, and turned into an entranceway which led to a flight of stairs, stairs which were musty and dark with the grime of years. They showed no sign of paint or care. Cobwebs were in the corners. They led up to a dark and gloomy hallway.

  Sidney Zoom, the police dog at his side, ascended those stairs with an unhurried gait. His entrance to the building was not unnoticed.

  The building had once contained offices of the cheaper sort. Some of the doors still bore signs which indicated the occupations of the previous tenants. One and all they were the sort of occupations which required plenty of space at a very low rental.

  The offices were now vacant. Some of the doors stood open, disclosing rooms which were littered with refuse. Some of the doors were closed. One was locked.

  Sidney Zoom gave some attention to that locked door. He produced a skeleton key from his pocket and opened the door. He went into the room.

  The litter in this room was not as bad as the litter in the other rooms. There was even a chair in the room. It was rather a run-down chair, to be sure, but a chair, nevertheless, and it was faced in such a position that a person sitting in it would be facing the window of the room on an angle.

  The window of that room was grimy with dust, dirt and cobwebs. The sash had once been varnished, but the varnish had deteriorated into dirty lumps which showed only a faint trace of gloss. Dust had settled upon sash and sill.

  Sidney Zoom left the door open behind him. He deposited himself in the rickety chair, took a cigarette from a pocket case, lit it, sat smoking, apparently without a single thing to do other than to enter the deserted offices of vacant buildings and while away the morning hours.

  The police dog, sniffing around him at the litter of the room, regarded his master with curious, attentive eyes, then flung himself upon the bare floor, and settled his head upon his paws.

  For several minutes they remained in this position, the man on the chair, smoking, the dog on the floor sleeping.

  Then the keen ears of the dog caught some sound. He raised his head and cocked his ears. He glanced at his master with yellow eyes that were suddenly hard and alert. Then he gave a low growl.

  Sidney Zoom heard that warning signal. He got to his feet. “Steady, Rip,” he said. “Don’t move. Keep quiet. It’s all right.”

  Sidney Zoom went to the dust-covered sash of the window. He took his fingers and pressed them into the dust of the sash, put the tips down on the sill. The fingers left very plain prints in the dust. He pressed a finger against the glass of the window. Then he took a small box from his pocket, opened the lid, and disclosed a yellow powder, a chrome which is particularly efficacious in bringing out the distinguishing marks of latent finger-prints.

  The police dog growled once more, ominously.

  Steps sounded in the outer corridor of the vacant office building. The steps were audible, yet cautious, the sort of steps a man would make who was of heavy build, yet was trying to walk cautiously.

  Sidney Zoom quieted the dog once more, ordered him to stay where he was, no matter what happened. Then he turned his attention to the finger-print on the window. He opened a little book, and started sketching.

  A figure bulked in the doorway.

  A booming voice suddenly cut the silence. “If that dog attacks me I’ll shoot him!”

  CHAPTER VII

  The Vanishing Shell

  SIDNEY ZOOM gave a convulsive start, the start of a man who is absorbed in work and fancies that he is alone, yet who is suddenly surprised by the sound of a human voice.

  He turned and stared at the big man in the doorway.

  The man had a gun in his right hand, a wide-brimmed black hat on his head, a gold shield on his vest, and a left eye which was almost closed, and which had turned a very deep shade of black. The gun he held was a heavy automatic.

  “The dog,” said Sidney Zoom, “will not bother you unless you bother him. And may I ask what you’re doing here with a drawn gun?”

  The man held Zoom with his eyes, the one steady, granite hard and baleful, the other bloodshot, rimmed by flesh of greenish black.

  “I’m here,” growled the man, “to find out what the devil you’re doing here. This building has been condemned. You’ve no business here. What’s more, this door was locked. You’ve evidently picked that lock. That’s breaking and entering, and that’s a penal offense.”

  Sidney Zoom raised his eyebrows.

  “But there was nothing in here, and I haven’t any felonious intent.” The heavy-set man rumbled his answer.

  “That’s got nothing to do with it. Technically, you’re guilty. You broke and entered.” Zoom pursed his lips, thinking over the man’s words.

  “You’re an officer?” he asked.

  “Yes. Frink, head of the county attorney’s investigation squad. Now you tell me what you’re doing here.”

  Sidney Zoom spoke rapidly.

  “I was figuring on renting an office here.”

  “What’s your business?”

  “I haven’t any. But I was contemplating opening up an office as a private investigator.” Frink scowled, moved purposefully forward.

  “All right. Now we’ll get down to brass tacks. You ain’t going to open up any office here. You ain’t going to do any private investigating here. You ain’t even going to stay here. You’re going right back to that nice little boat of yours and cast off the mooring lines and get out of here and stay out of here.”

  Sidney Zoom stared about him in a bewildered manner.

  “Why—why, I never was talked to like that in my life. Why can’t I stay here?”

  The head of the investigators was now sure of his ground. He moved forward in a bullying manner.

  “Because you’re a confounded nuisance. That’s why. You busted in on Sam Gilvert an hour or so ago and insulted him by having your dog go over and smell him. You were prowling around the streets last night … and somebody broke into the county attorney’s office and tried to steal some papers. It was a woman. I cornered her, and somebody smashed me with a club and knocked me out. I don’t know who it was.”

  Sidney Zoom raised his eyebrows.

  “But what’s that got to do with me? Why should I leave town? You don’t suspect that I hit you with a club, do you?”

  The eye of George Frink which was not discolored hardened into an icy stare. “If I did think that you did it,” he growled, “I’d …”

  He didn’t finish his threat.

  His eyes slithered away from Sidney Zoom’s, came to rest on the finger-print, colored with the yellow stain.

  “What you doing here?” he asked.

  “Just looking out of the window,” said Sidney Zoom.

  And, as though to give some atmosphere of truth to his statement, he turned, and peered through the dusty, cobwebby glass of the window.

  The main street showed below him, across the street, some forty yards up, were the entrances to the county attorney’s office, the windows of the room in which Strome had been killed.

  As Sidney Zoom watched, a compact group of men, carrying brief cases, emerged from the entrance to the office building. Carl Purcell, the new county attorney, and his assistants were about to go to the courthouse to carry on the trial of James Crandall, charged with the crime of murder in the first degree.

  Frink’s voice was sneering.

  “Yeah, you was lookin’ out of the window all right! And I suppose you smeared that yellow chrome over that finger-print to help you see out! What’s a finger-print on a window down in this building got to do with the murder of Frank Strome?”

  Sidney Zoom suddenly became confidential.

  “If I should tell you, would you keep it a secret? And if it sounds plausible, could I continue to remain here and carry on my investigations?”

  Frink poised the gun in his hand, stole a glance at the police dog.

  “Go ahead,” he said. “I’ll listen to anything you’ve got to say, but I won’t make any promises.”

  Sidney Zoom spoke rapidly, and in a low tone.

  “Very well. The account of the shooting, as we have it, is impossible. No one heard the sound of the fatal shot. That’s out of the question. The theory of the prosecution is that the noise made by the exploding bomb of the publicity car on the unemployment drive drowned out the noise of the shot.

  “That’s foolish. People who were in the next office would have heard that shot as being distinct from the explosion of the bomb. Moreover, there wasn’t any exploded shell found in the office of the murdered man. Now the gun that was found in there was an automatic. The automatic mechanism would have ejected the empty shell as soon as the weapon was fired. Yet that shell wasn’t found. Of course, the murderer might have crawled around on the floor, picking up the empty shell, but there was no reason for him to do so.

  “On the other hand, had that murderer been intent upon removing evidence, he would have undoubtedly taken the automatic from the room with him. If Crandall killed that man, it would have been utterly incredible that he would have gone to the bother of taking the shell from the room, yet leaving the weapon which could have been traced to him.”

  Sidney Zoom regarded the investigator questioningly. “What’s your theory?” asked Frink.

  Zoom lowered his tone, as though giving a sacred confidence.

  “That the murderer didn’t kill Strome in his office at all. That the murderer came down here, opened this window and waited. That the stage was set in Strome’s office. That the publicity car came by here, setting off bombs. That the murderer rested an automatic on the sill of the window, and fired through the open window of Strome’s office, killing Strome.”

  Frink scowled meditatively. “Why this office?”

  “Because the door was locked. The murderer had to lie in wait with a drawn gun. Naturally, he wouldn’t want to be observed by some person who might chance to come up in the building. So he took pains to see that the door behind him was closed and locked. Then it would have been only natural for him to have locked the door behind him when he left.”

  Frink walked to the window, stared.

  “Then this would be the finger-print of the murderer?”

  “Yes.”

  “What makes you think the window in Strome’s office was open?”

  “Because the papers were scattered all over the floor. It has been the theory of the prosecution that the murderer, making a hasty search for some paper, threw the papers on the desk all over the floor. More natural, the window had been left open, a sudden wind blew the papers over the floor, and the window was subsequently closed before the arrival of the police.”

  “Then the window would have been closed … Good Heavens, man! Do you know what your charges imply? They mean that Carl Purcell must have been an accessory!”

  CHAPTER VIII

  The Finger-print on the Window

  SIDNEY ZOOM nodded, casually.

  “Of course. That’s self-evident, even if we can’t prove who it was that did the actual killing. You’ll remember that Strome mentioned the threatening letter he had received was the second threat he had received from Crandall. Yet, when they came to search for the first threat, it couldn’t be found. What undoubtedly happened was that Purcell, seeing the original threat wasn’t dated, simply took it from the files, put it in an envelope, and remailed it to the county attorney.

  “The same thing’s true of the gun. It was purchased before Crandall was sent to prison. He’d hardly have had that gun with him all the time he was in prison. It’s natural to suppose, therefore, that the gun had been taken from him by the authorities at the time of his first arrest. Since his crime wasn’t one of violence, the gun naturally wasn’t introduced in evidence. The authorities probably even forgot that they had such a gun. But Purcell could have taken it, secreted it, and planted it for evidence. “Purcell isn’t a gunman. Therefore, he forgot that he should have planted an

  empty shell to make the murder appear convincing.” Frink whistled.

  “Man alive, but you go after big game when you start. What possible motive would Purcell have had to kill Strome?”

  Sidney Zoom smiled.

  “The motive of greed and of gain. Charges were about to be placed against Sam Gilvert, the banker. The file in that case disappeared. Purcell was a deputy. Now he is the county attorney. He inherited the office, so to speak.”

  Frink shook his head.

  “No. Your motive isn’t strong enough to get you anywhere. You insinuate that Gilvert paid Purcell to sneak the papers out of the file, that Purcell got that money, and that he was afraid of discovery, so he wanted to cover up that theft. Then you insinuate that he wanted to get the job of his superior officer, and so he murdered him. That’s far-fetched. It isn’t a strong enough motive.”

  “There’s logic in that,” Zoom said. “Yet we know that the crime couldn’t have been committed the way Purcell claims. We know that, if it wasn’t committed in that manner, then Purcell must be trying to conceal the manner in which it actually was committed.

  “But we can let Purcell go for the minute. We’re on the trail of the real killer down here. I think this fingerprint will give us sufficient evidence. Somewhere around here, in the litter of rubbish around the room, may be the empty shell from the gun that really killed Strome.

  “That must have been an automatic of the same calibre as the one in the office, the one that was found there. The distance isn’t over thirty yards or so in a direct line. A good shot could have hit a mark the size of a man’s body at that distance. In fact, he could have even picked the exact spot on the body that he intended to hit.”

  The chief investigator for the county attorney’s office put the automatic he held back in its shoulder holster.

  “Guy,” he said, “you win. We’ll find out more as we go along, but you sure have got the case doped out so it sounds reasonable to me. I’m going to cooperate with you and give you all the assistance I can.

  “But this is a small county. We’re messing around with some pretty big men when we start after Purcell and Sam Gilvert. We’ve got to be absolutely certain that we’re going to make a case before we even breathe a word about it.”

  “Naturally,” Zoom observed, “we will not go running into court and shooting off our faces. We’ll collect the evidence. In time, if we can, to save Crandall from conviction, we’ll announce that evidence. If we haven’t built up a case, we’ll let him be convicted, and then get a pardon from the governor.”

  Frink drummed upon the back of the chair with the fingers of his right hand. His eyes narrowed to slits.

  “Listen,” he said, “we’ve got to get those finger-prints photographed. That’s the first thing. Then we’ll have to pull the whole window out and take it down to the vault where we can keep it for the jury to look at.”

  Sidney Zoom nodded.

  “You got a camera?” asked Frink, “one that’ll take finger-prints?” Zoom shook his head ruefully.

  “I’m sorry. I certainly should have had one, but I was careless and neglected to include it with my things when I came down here.”

  “Okay,” said Frink, “it doesn’t make any difference. You go and get mine. I’ll stay here and watch the prints so I can testify afterwards that nothing happened to ’em, see? My office is on the lower floor of the courthouse. You’ll find a blond kid at the desk. She’ll give you the camera. Tell her that I sent you, and that I said to keep quiet about it afterwards. I don’t want a whole lot of talk around town about this thing before we crack it.”

  Zoom allowed himself to be dominated by the positive personality of the other. “Come, Rip,” he said to the dog, and left the room.

  But he did not descend the stairs. Instead, he waited in the corridor, motioning the dog to silence. For a good ten seconds he stood so, and then he returned to the door, gently turned the knob, and pushed the door open.

  Frink was standing by the window, his face grave with concern. His right hand was extended. He was staring at the whorls of the fingertips with a magnifying glass. Then, from time to time, he would check these with the finger-print on the glass.

  Sidney Zoom betrayed his presence by a low laugh. It was a mirthless laugh of hollow mockery, and there was challenge in it.

  Frink whirled.

  It took him one swift instant to take in the situation. Then his hand flicked to the holster where he kept his weapon.

  Sidney Zoom spoke casually. “Take him, Rip.”

  The dog had waited patiently for that moment. Twice when he would have defended his master against this man, he had been restrained by a command. Now the dog went across the room, belly to the floor, like a tawny streak. And then he was in the air.

  Frink fired, once, and he might as well have taken a snapshot at a streak of lightning. The dog’s teeth closed on the wrist of the gun arm. The dog’s weight hurled itself in that peculiar twisting motion which is taught to police dogs, as a part of their training, on the continent. Frink screamed with pain. The gun thudded to the floor.

  Sidney Zoom rushed in and grabbed the left arm.

  “All right, Rip,” he said.

  The dog dropped to the floor. Sidney Zoom’s right hand snatched the handcuffs from the investigator’s hip pocket. With a swift dexterity, he flipped the handcuff over the left wrist.

  “The other hand,” he rasped.

  The investigator flung his weight against Sidney Zoom in a lunging attack, halted as a deep-throated, ominous growl came from the dog on the floor.

  “You can either give me that wrist, or the dog will get it for me,” said Sidney Zoom.

  The investigator’s face was sallow. Perspiration beaded his forehead. He extended his wrist, with the prints of the dog’s fangs still imbedded in the skin, through which red drops welled slowly.