"What about it, commissioner?" queried Joe. "Shall I keep on grilling him until he cracks?" Weston was starting to nod, when he heard Cranston speak. They held a buzzed conversation; finally the commissioner nodded.

"All right, Cranston," he said, indulgently. "If you have a suggestion, we shall be glad to hear it."

Calmly, The Shadow strode to the center of the floor. In Cranston's idle style, he looked at the spot where Rendrew had lain dead, then glanced about the room. He looked at Cardona's clues, together with the forged letter that Dwight claimed was sent to him.

"My suggestion, commissioner," he said, calmly, "is that we should consider Kelden's story as if it actually happened; then look for any flaws in it."

Weston beamed. He liked that sort of thing. He had always emphasized the value of deductive reasoning; this might be good instruction for Joe Cardona.

If Cranston brought out some point that would clinch the case against Dwight Kelden, much valuable time would be saved.

"LET us a.s.sume" - Cranston's tone was casual - "that Kelden did receive this letter. That brings another party into the case; the person who actually forged it. Let us determine what else that person could have done."

He picked up the desk calendar and its torn page, then asked if he could take two other leaves from it. Weston agreed; detaching two sheets, Cranston held them close, together and gave a quick tear. He pa.s.sed the torn leaves to the commissioner.

"You will notice," observed The Shadow, in Cranston's tone, "that the torn portions of those sheets are interchangeable: Which proves that the torn piece from Rendrew's daily calendar might have come from some other sheet; let us say, for instance, from an old calendar of the same make."

Helene's eyes were very wide. She understood, at last. A year ago, when Dwight Kelden had been East, Adam Rendrew had probably made a notation on his calendar. Some one had taken that old date sheet, placed it on the present year's calendar, and used the very system just demonstrated by Cranston!

Adam Rendrew had not expected his nephew, Dwight Kelden, to pay that visit at nine fifteen, on Tuesday, the tenth. Someone had faked it to appear as if he had!

"As for the eyegla.s.s wiper," she heard Cranston say, "it interested me considerably, commissioner. Today, I sent a taxi driver into Weeker & Sons to ask for one. Here it is" - he produced a wiper from his pocket - "along with an airplane schedule" - he was drawing out the object mentioned - "that I took from a timetable rack in a hotel.

"Anyone else could have obtained such items, to serve as evidence against Dwight Kelden. Whether or not someone did, we must judge later. So far, we have simply failed to detect anything wrong with Kelden's story."

THERE was a long pause, during which two persons stared at Lamont Cranston with expressions of thanks as well as admiration. Those two were Dwight Kelden and Helene Graymond. Not that others were lacking in appreciation; both Weston and Cardona showed plenty. There was a question, though, that they couldn't fail to ask. It was the commissioner who put it: "But who other than Kelden could have shot Rendrew?"

In Cranston's style, The Shadow looked around the room. He took Rendrew'sposition and faced the door.

"According to your statement" - the question was put to Dwight - "your uncle backed into the room?"

Dwight gave a positive nod.

"Yet he was shot in the back" - Cranston had turned toward the bookcase - "which means that the bullet must have come from here!"

With a single sweep, he pulled half a dozen volumes from a shelf.

Reaching deep, The Shadow rapped his knuckles against metal. He leaned back, to look into the s.p.a.ce; then eyed the thick wall against which the bookcase stood.

"An open hot-air register," he announced. "Suppose a gun had been there, commissioner, pointed out through the loose grating on the front. A gun equipped with a photoelectric cell - a mechanical eye, issuing a line of black light straight across the room.

"Rendrew, backing into the path, would have interrupted the beam. A shot from the gun, so aimed that the victim could not escape it, would have found Rendrew's spine and killed him. It would account, too, for the shot that Kelden heard."

The theory left Joe Cardona staring, until ideas began to strike him.

Therewith, he began to quiz Lamont Cranston.

"Why didn't anyone see the gun?"

"Let me have your own revolver, inspector."

Receiving the weapon, The Shadow replaced the books, then pressed the gun barrel between the center ones. He showed that they formed a gap, though the gun muzzle was deep from sight.

"But what happened when the gun was fired?"

"The weapon recoiled," returned The Shadow, drawing out Cardona's gun.

"The books pressed together" - he pointed, by way of ill.u.s.tration - "and the revolver dropped down the register pipe."

Cardona's gun thudded the floor as The Shadow's fingers released it.

"It sounds good," admitted Cardona. "Only that beam of black light you talk about must have had a receiving device at the other end of it."

Cardona paused; he was following Cranston's gaze, toward the floor lamp near the door. Stepping there, The Shadow removed the unlighted bulb and smashed it. In its interior was the very apparatus that Cardona had asked about!

This time, the silence was ended by a detective shouting from the stairway: "Mr. Cranston's car is here, inspector!"

"I am very sorry" - The Shadow was Cranston to perfection, as he bowed to the persons present - "but I must be going home. My physician has ordered it, because of my recent accident. So good night" - he paused, stepped up to Dwight Kelden and gripped the young man's right hand, lifting it with the handcuffs - "and good luck to you, Kelden!"

They saw Cranston walk from the room, heard him go down the stairs. Then came the closing of the front door, audible through the echoing pa.s.sage of the big mansion. To all, except one person, that was the final sound of Cranston's departure.

Helene Graymond fancied that she heard one token more: a strange, whispered tone of mirth, that must have wakened itself to life from deep within her memory.

The laugh of The Shadow!

CHAPTER XIX FALSE BRINGS TRUE.

OUT of a mental whirl, Helene Graymond began to realize the depth of The Shadow's methods. It was he, not Cranston - the girl was still too bewildered to link the two - who had first divined that the clues against Dwight were planted.

She remembered how The Shadow had paced this room and made his calculations. He had been trying, then, to visualize a way whereby Adam Rendrew could have been slain almost in Dwight's presence, without the action of a human hand.

In effect, The Shadow had let his own brain work along the line that the murderer had followed. Step by step, he had built up a logical way to arrange the death of a person entering this room, and his final findings had checked!

Of course, the real murderer had been smart enough to remove the evidence of crime. He had reclaimed the death gun from the bottom of the hot-air pipe.

He had disposed of the mechanical eye that was attached to it, also the wire that must have extended down the pipe to a light socket, probably behind the bottom of the pipe in the cellar.

He had taken the two books also, because they were scorched by the flame from the revolver muzzle; and he had replaced the special light bulb with an ordinary one. He had made two mistakes, however, slight though they seemed.

The bulb that the killer had put in the lamp socket was a new one, that lighted when the switch was pressed. The murderer had also left the last-year's calendar in the office closet, probably supposed that no one would ever look for its missing page.

Obviously, The Shadow could not have obtained the evidence that the killer had destroyed. So he had adopted the neat plan of providing similar items: the contents of the package that had been delivered at the house!

It was fair enough, under the circ.u.mstances. The murderer had framed Dwight Kelden by planting clues against him. The only way to nullify those tangible bits of evidence was to plant other clues against the murderer!

The Shadow had done exactly that. He had nullified false with false. But the objects that The Shadow had provided were legitimate subst.i.tutes for the ones that the murderer had removed. From the false, The Shadow had proven the true.

One thing puzzled Helene. She felt sure The Shadow had intended to plant more evidence than the light bulb. The books should have gone on their shelf; the wire, with its electric light attachment, at the bottom of the hot-air shaft.

Why hadn't The Shadow gone through with those arrangements?

Suddenly, Helene had the answer. The Shadow had made his plans before Froy's death. Somehow, the servant had meddled into matters, and thereby produced new complications.

Joe Cardona was reviewing that very fact. He was asking Dwight: "If you didn't murder Rendrew, why did you kill Froy?"

"I didn't!" returned Dwight. "Froy answered my first phone call. I said I was at the Espon and gave the room number, even though I didn't mention my name. He must have guessed who I was. Knowing the law was after me, he figured I would pay for silence. But I wasn't there when he came. Somebody else killed him."

From somewhere, Helene seemed to hear a whisper. It might have been her imagination, yet it had a tone that she remembered. The voice of The Shadow: "Remember the box!"

Helene nodded. Before Cardona could quiz Dwight further, she interrupted, to announce: "Froy left a metal box with me before he left. He said its contents were important. I put it in the office safe."

CARDONA told the girl to come along with him and open the safe, so he could get the box. Soon, they returned; Cardona was carrying the box, and Helene was sure that it was heavier than when she had placed it in the safe.

Cardona unclamped the box in front of Weston, then raised the lid.

Inside were the other objects that Cranston had pictured: a wire with a photoelectric attachment; two books, matching a pair on the shelf, except that they were scorched by streaks of gun flame!

The last-year's calendar was also in the box. Thumbing it, Cardona looked for the date of Dwight's previous visit East. The page was missing; the fact fitted with Cranston's theory that an old sheet and a new had been torn as one.

Then Cardona found a bullet, its nose mashed from an impact.

"It looks like a .32 caliber," admitted the inspector. "I guess this was the bullet you fired through the window, Kelden. Froy was pretty smart to go out and hunt it up."

Helene was understanding more. With Froy dead, The Shadow had decided to stow the a.s.sembled evidence in the servant's strong box, to make it look as if Froy had gathered the various clues. That ruse added an authentic touch; the clues seemed more valid than if they had come from an unknown source.

But what had Froy left in the box?

One thing only - a note that Cardona had just found. Reading it, Cardona announced the high spots. The note said, in effect, that Froy was going to the Espon Hotel to hunt for Dwight Kelden, hoping to gain a trail for the law. He was leaving the note as a protection. He intended to tell Dwight that he had made provision to insure a safe return.

Obviously, Froy had gone to demand money; though he didn't say so in the note. He must have supposed that Dwight was actually a murderer, and hence had regarded his trip as dangerous. But Cardona, influenced by the evidence that The Shadow had later added to the box, was ready with a theory of his own: "Froy wanted to sell you this stuff," he said to Dwight. "He knew that someone else had planted it to kill Rendrew. I guess it clears you, Kelden - provided, of course, that it works."

Deciding that he ought to test the apparatus, the inspector promptly set to work. He removed the front of the register, clamped the electric eye on the death gun. Holding the muzzle through the grille, Cardona put the register front back in place.

If he had released the revolver, it would have dropped. From that, Cardona guessed the real purpose of the books. With Helene helping him, he put them into place, and the pressure of the two central volumes held the gun right where it was.

Cardona was using the two new books, to learn if they would scorch as expected. Rather than go down to the cellar, he fished for the cord attached to the electric eye, brought it over the books and plugged it into the lamp on Rendrew's desk.

Picking up the dummy light bulb that Cranston had broken, Cardona studied the reception apparatus and gave a satisfied nod.

"This will work, anyway," he declared. "The gla.s.s part of the bulb was only there to hide it."

He screwed the broken bulb into the socket, tilted the gun muzzle slightly, until its aim was correct. Motioning everyone to the side of the room near the door, Cardona reached out and turned the lamp switch.

With the click, a thin black beam appeared, forming a pencil linestraight from the book-clamped revolver to the broken bulb in the floor lamp!

"Cranston was right!" announced Weston. "Black light, that couldn't have been seen in darkness! Very well, inspector, you may cut the beam and complete the test. Use any suitable object - a table, for instance; since all the chairs are occupied."

WITNESSES to that dramatic scene were tense, while Cardona was picking up a light table that stood in the corner. Then, when he had almost reached the center of the room, Cardona added a new element to the situation.

Holding the table by one leg, he lowered its top to the floor and looked at the faces that were watching him.

Finally, Cardona met Weston's gaze, and questioned: "Tell me, commissioner: who do you think killed Adam Rendrew?"

"Why, Froy, of course!" voiced Weston, suddenly. "He left all the equipment in the box. We should have thought of that before, inspector."

"It couldn't have been Froy," a.s.serted Cardona. "He wouldn't have left the equipment with the note. If he'd been the murderer, he wouldn't have been scared of Kelden. Besides, somebody killed Froy, too. That person, commissioner, must be here in this room!"

The logic was solid. So absolute, that Helene realized that The Shadow did not have to be here to a.s.sert it. He had known, of course, that the fact would sooner or later strike home to Joe Cardona. The inspector's gaze rested on Helene, as though he momentarily considered her as a possible suspect; then his eyes fixed elsewhere.

Louise Dreller gave a shriek. Cardona was looking right at her. The blonde began to wave her arms excitedly, the sleeves of her silk kimono flapping like a b.u.t.terfly's wings.

"I didn't kill them - either of them!"

"We'll forget you for a while," growled Cardona. "You wouldn't know what a photoelectric cell was! But your brother here -"

His gaze was on Archie, who gave a pitiful wince.

"You and Silk Elredge were up to blackmail, weren't you?"

Archie nodded at Cardona's question; then found his voice, which was more whiny than ever.

"That was all," insisted Archie. "We didn't want to murder Uncle Adam.

Silk said a shakedown was the system."

"You got money from your uncle's death."

"Only a little income. Silk wanted more, and so did I. We'd have been crazy if we'd gone through with a murder. It ruined our plans when Uncle Adam died. Besides -"

Archie paused; an idea had struck him, and he expressed it with great eagerness.

"Besides, I couldn't have killed Froy tonight. I've got an alibi! I was at the poker game, with the fellows you talked to the other night. They'll all tell you that I didn't leave the place until Johnny came to get me -"

"Quite true!" IT was John Osman who provided the interruption. Cardona swung about, and faces turned with him. All eyes were looking at a gun that Osman had drawn.

Only Dwight Kelden found his voice, to exclaim: "That's my gun! The one that was in my suitcase!"

"Of course," sneered Osman. "I found Froy's box tonight, while Helene was upstairs. Only the note was in it, at the time. After I left the house, I phoned the police and told them where you were. I went to the Hotel Espon myself, intending to take some credit for your capture.

"Froy was there ahead of me. He had your gun, so I shot him with the one I.

carried - the same revolver that killed Rendrew. I left the .38 where you would pick it up, and took the .32 with me. I was starting down the stairs when you stepped out of the elevator. You walked right into the new trap I'd laid for you."