Simultaneously, Cardona, peering toward the wall, could see a little panel moving upward. This sliding device had been concealed behind the radiator.
“Easy,” urged Biscayne. “Don’t let these sections spring back!”
The panel reached the top of the opening, as the radiator portions reached a half-opened angle. The moving slide clicked.
There was a sharp report from a pistol. A puff of smoke whisked from the space behind the raised panel.
The sound was startling. Cardona gripped his half of the radiator. Biscayne did the same.
The watching men stared. But as the smoke thinned, all eyes turned instinctively to the other end of the room.
For their ears had heard an answering sound — a sharp crack that had followed the report of the gun. It had come with the pistol shot, sharper even than the explosion from behind the radiator.
The clay bust of Silas Harshaw had been shattered by the bullet from the hidden weapon. Its broken pieces were upon the footstool and upon the floor.
Amid the chunks of hardened clay lay two compactly folded wads of paper.
Biscayne called to Wilhelm to hold the one side of the radiator. Springing across the room, the professor seized the wads of paper.
He rapidly unfolded one and thrust it in the hands of Commissioner Weston.
“It looks like plans,” said the commissioner. “Diagrams, traced on thin paper—”
Biscayne was opening the other wad. His spectacled eyes peered eagerly. He showed it to Weston.
The paper bore a written statement that was headed by a list of names.
“Harshaw’s enemies,” declared Biscayne soberly. “The plans — the men he feared — they were in his head. That is what he said.”
Dramatically, Biscayne pointed to the broken chunks of clay that had composed the modeled head of Silas Harshaw.
The professor softly repeated the statement that he had made before.
“In Silas Harshaw’s head!”
CHAPTER XXI
THE HIDDEN TRAP
PROFESSOR ROGER BISCAYNE was reading the list of names from the sheet of paper that had been discovered.
All were listening, including Cardona, although the detective appeared to be otherwise engaged.
Wedged between the sections of the radiator, he was examining the space that had been hewn in the wall.
“Here are the names,” declared Biscayne. “Louis Glenn. Thomas Sutton. James Throckmorton. Arthur Wilhelm.
“Listen to this statement, written beneath:
“I, Silas Harshaw, sound of mind, do declare and proclaim these men as my enemies.
“Louis Glenn urged me to spend my little pittance in stock that proved worthless. Thomas Sutton refused to listen to me, when I told him of my great invention.
“James Throckmorton questioned me suspiciously, and demanded that I tell him all my plans. Arthur Wilhelm furnished me with funds, but did so grudgingly, expecting much from little.
“I believe that any one of these men would steal my brains if they could do so.
“Hence if any one of them should fall into the snare that I have laid, his death will be on his own head.
“Let them beware! Alive or dead, I can thwart their plans of theft!”
“The man was crazy!” exclaimed Wilhelm. “I would have given him all the money he wanted, if he had shown some results. But I wasn’t going to throw my cash away.
“To think of it! He tried to kill me!” Joe Cardona was calling from the spot beside the window.
Biscayne placed the paper in the hands of the commissioner, and hurried to the other end of the room. The others followed.
Peering into the open space, they saw the muzzle of a revolver. The weapon had been mounted at the back of the space, set between braces.
It was connected to the sliding panel by a neatly fashioned contrivance that was to set to press the trigger of the gun every time the slide came up.
Cardona removed the gun and brought it out. As he stepped away, he released pressure on the sides of the radiator, and they swung back to their original position.
A sharp click told that the sections had automatically locked.
“Five chambers,” remarked Cardona. “Wonder where the old guy dug up this rod. A .32. Hm-m-m. Four cartridges used.
“One for Harshaw. One for Max Parker. One just now. Wonder when the other was fired.”
“That hardly matters,” said Biscayne. “Let’s look in that compartment again.”
He pulled the knob of the radiator. This time, Cardona opened the metal sections with impunity, for the menace had been removed.
He discovered a small stack of letters and some papers. Also another object, which Cardona seized with a sharp exclamation.
It was a cigarette box, bearing the name, “Istanbul.”
“The brand that Glenn smoked!” proclaimed Cardona.
Biscayne was looking at the envelopes. There were only three.
One was addressed to Louis Glenn; the second to James Throckmorton; the third to Arthur Wilhelm. They were written in a scrawl — a scrawl which Cardona recognized as the writing on the envelope which had been found by Thomas Sutton’s wastebasket.
That envelope had borne the instructions to seek the gold-headed cane in the fatal closet beneath the stairs.
The envelopes were not sealed. Biscayne read the letter addressed to Louis Glenn. It was full of vague remarks Biscayne quoted in part:
“We have not met for years… You have forgotten me… You made me lose my money, but I shall be wealthy, now! My brain will bring me millions…”
Laying the letter aside, Biscayne took the one addressed to James Throckmorton. He read these statements:
“You wanted to know about my inventions… They are completed now… The one will bring me millions. You will know all about it then…”
The letter to Wilhelm carried a different tone as Biscayne read it:
“My task is done… My model lies complete, where it is safe… It is at my home…”
“Here’s another letter,” remarked Cardona, going through the odd papers which he had found. “It’s to Thomas Sutton, but it has no envelope. Listen. “It says that Sutton had no faith; that he will hear great things from the man whom he had ignored.”
Biscayne nodded as he received the letter and quoted aloud:
“My visits to you were in vain. You failed me. All have been against me… I have prevailed… You missed your greatest opportunity…”
Cardona was pondering. He smacked his fist against his other palm and looked up at his companions.
“These letters were going to be mailed,” he declared. “The old man must have changed his mind. He sent Thomas Sutton a typed letter, but used the envelope that he had prepared for this one.
“All those death notes must have come from Harshaw — even the one about himself! But who sent them?”
“Harshaw sent them,” declared Biscayne suddenly. “Sent them from this apartment. He must have intended to send these letters, too — probably while he was away.
“When did you advise him to take a trip, Doctor Fredericks?”
“Often,” said the physician. “He never wanted to go. He said he was afraid to leave. When I urged him, he said that he would make plans so he could go.
“When I finally told him he must go away, he agreed to leave at once—”
“That’s it!” exclaimed Biscayne. “He had these letters ready. He wanted them to be delivered while he was away, so that his enemies would think he was at home.
“Then, with death staring at him, he turned to another scheme more insidious than idle threats or inferences.
“He arranged the killings — and sent the death notes!”