The light turned about the room. In its glare appeared the shadow of the man who held it - a long shadow that came and went like a specter of the night. Then the light was turned off. The smaller flash took its place.
The man with the light passed through an almost invisible opening in the curtain and cautiously entered a smaller room, with drawn shades and shuttered windows. Here was a curtained niche. The investigator spread the curtains and discovered a broad, old-fashioned windowsill. It was an ideal spot where a man could hide.
The light moved across the room. It centered on a desk upon which lay a pile of papers. One by one the prying hand investigated them. It found nothing of importance.
Then it came to a calendar. One date was conspicuous. That was the thirtieth of June. Around it was a small penciled ring. It must signify an appointment.
June the thirtieth was tomorrow!
The man with the light continued his mysterious investigation. He confined his efforts to the first floor.
There was a stairway to the second; also one to the cellar. Both were protected by heavy, double-locked doors.
The man who had made the search continued no further. He was satisfied after he had discovered a locked closet and had opened it. The closet contained an array of firearms on one shelf. Beneath the shelf, at the bottom of the closet, were hollow shells and bits of mechanism. They were the appliances of a bomb maker. The invisible man laughed softly, in the darkness.
He closed the door and carefully relocked it. The light moved back toward the rear of the house. It disappeared. A form slipped through the window. The sash was lowered noiselessly. The barred grating was replaced and fastened in the darkness.
The next day Detective Joe Cardona received a carefully drawn diagram, showing every detail of the ground floor of the old house with the barred windows.
Cardona was sitting at his desk in headquarters when he received the communication. While he was still puzzling over it, the telephone rang. He answered and listened intently as a low, strangely familiar voice came over the wire.
'You have received a diagram,' came the voice. 'It is there before you now.'
'Yes,' replied Cardona in amazement.
'Now I must have your word that you will follow the directions that I give you.'
'Go on,' interposed Cardona. 'I promise!'
'The diagram shows the ground-floor plan of the quarters of the man behind the bomb outrages,' the voice continued.
Cardona was too startled to reply.
'The large central room is the danger spot,' added the voice. 'That is where he lures his victims.
'The place is a trap. The walls are covered with jet-black curtains. The room is wired with electric current.
'There will be a meeting there tonight,' came the voice in an impressive tone. 'The criminal himself will be present. You can capture him - and with him evidence that will prove his guilt.'
'What evidence?'
'Bombs!' the voice was sibilant. 'Partly finished bombs! But remember, your enemy is dangerous. Unless you follow my plans exactly, you will not capture him. Do you understand?'
'Yes,' replied Cardona.
'Wait in back of the house,' came the voice. 'Be there after dark with a squad of men. Lie low. Give no sign of your presence. Do you note the window marked with a tiny X?'
'Yes.'
'Enter there. Advance to the door of the central room. Go no farther. That is the danger zone. Wait there. The escaping criminal will be forced to choose that exit. And that criminal will be - The Black Master!'
'And who are you?'
'A friend,' said the voice with a hollow, whispered laugh. 'I, too, shall be somewhere in the inner room, where I can trap the enemy. I shall force him into your hands! Once you have captured him, you can search the house.'
'I understand,' said Cardona grimly. 'When shall I enter with my men?'
'When you receive my signal, a shot fired from within the house. Then The Black Master will know of my presence; but he will be at my mercy.'
The whole scheme sounded fanciful to Cardona; nevertheless, the impressiveness of that sibilant voice made him realize that this was not a hoax.
'I am counting on you,' said the voice, 'because this man is a mastermind. He must be captured, and his identity revealed - otherwise innocent men will go to their deaths. Do you understand?'
'Yes. Where is the house?'
The laughter that came over the wire was soft with mockery. It made Cardona realize the ingenuity of his informant. Without the location of the house, all these plans were useless.
'That,' said the voice, 'is something that you will learn only if you again promise to obey my instructions to the final detail.
'No matter what happens - no matter what you may suspect or see, you must not move or mention your plans until you receive my signal. Do you promise?'
'Yes,' agreed Cardona with sincerity.
'Then take down this address.'
Cardona scrawled the final data upon a sheet of paper. He had hardly finished when he heard the click of the receiver at the other end.
The detective pocketed the address that he had written, together with the diagram. When Joe Cardona agreed upon any plan, he adhered to it. He knew well who had uttered those mysterious words over the telephone.
The Shadow!
'Tonight!' muttered Joe Cardona. 'Tonight!'
He smiled in anticipation. It was the kind of work that Joe Cardona liked. He had full authority to choose his men and go on any quest that he might choose. He thought of Inspector Burke's surprise tomorrow.
This talk of a Black Master was mysterious - but The Shadow was a man of mystery. He had guided Cardona in the past. Tonight, the detective knew, would reveal new and sensational results that might lead to a final solution of the crimes which had terrorized New York.
'Tonight!' repeated the detective. 'Until then, I keep mum!'
CHAPTER XIX. ENTER THE SHADOW
THE telephone rang again beside Joe Cardona's desk. Doctor Zerndorff was on the line.
'I would like to see you,' said the criminologist. 'It is very important! I cannot tell you now!'
Cardona glanced at his watch. It was still early in the afternoon.
He rode uptown to Zerndorff's apartment. There, Doctor Zerndorff smiled pleasantly.
'All is well, Herr Detective,' said Zerndorff. 'Those men we have captured, they are guilty, yes? We have finished our work - and it is to you that all the credit belongs. Yes, to you!'
'I guess we've cleaned them up, professor,' Cardona smiled. 'Only -' He stopped abruptly. He seemed to hear the voice of The Shadow, with its warning words.
'You think there are others, yes?' questioned Zerndorff.
'Perhaps,' said Cardona.
'How many?'
'There may be another man -'
'Impossible!' There was impatience in Zerndorff's declaration. 'Impossible! We have captured them all!'
Cardona became silent. He remembered his agreement with The Shadow. Yet this positiveness of Zerndorff made him wonder.
