What would happen when they crossed that streak of light? Riley imagined he knew. Verbeck felt sure that he knew. Muggs already imagined he heard the cracking of an automatic, grunts of pain, faced the whirlwind charge of a desperate, cornered man, fighting his way to freedom.

"Come out!" Riley commanded again. "Come-or we'll come in after you!"

Still no answer. Riley crouched and held the torch high above his head in his left hand, ready to touch the b.u.t.ton and send a shaft of light into the vault. In his right hand he held the automatic, safety catch off, ready to fire on the instant.

He touched the b.u.t.ton.

Light shot through the blackness and illuminated a pathway through the vault door and to the interior. From side to side Riley swung his light, expecting every instant to hear the shot he antic.i.p.ated. There was no man in the light's path, but it did not penetrate to the corners.

Riley expelled his breath in a great gasp of determination, and slipped forward. Verbeck and Muggs closed in. If the Black Star was waiting for them to rush, then the moment for the rush had arrived.

Muggs could endure the suspense no longer. His nerves were on edge. He gave a subdued squeal and sprang across the path of light, grasped the door, hurled it shut, twisted the handle.

"We've got him-got him!" he screeched.

Riley's light showed the perspiration standing out on his forehead in great globules.

"Why did you do that?" the detective demanded.

"We've got him! Turn on the lights! The police will be here in a minute, then he'll have no chance to escape!"

Riley would have had it otherwise, and Roger Verbeck had antic.i.p.ated having the Black Star in shackles by the time the police arrived, but that could not be helped now. Riley went around the room until he found the electric switch; he threw it, and the room was suddenly brilliant with light.

"Well, we've got him, anyway," Verbeck said. "The Black Star may be able to get into a vault, but I'll defy him to get out of that one except by the door."

"Yes, and he'll be dead before he gets out that way, if some one who can open that vault doesn't come soon. Where's a telephone?"

He saw one in a corner, and rushed toward it and gave the private number.

"That you, chief?" he asked. "This is Riley? Have you sent men? What's that-just started? Great Scott-- He did, eh? Say, chief, have the desk sergeant telephone to the manager of Jones & Co. to hurry down here.

We've got the Black Star locked in the vault, and have to get it unlocked. Yes-sure!"

He hung up the receiver and turned to the others.

"Men on the way," he said. "The chief says he just got the telephone message. Says the sergeant said he tried three phones near your place, and all of them had wires cut. Pretty smooth article, that Black Star-but we've got him! There they come now!"

From the distance came the sound of a siren, the clanging of a patrol-wagon bell. Then the pounding feet on the marble stairs, loud commands, and men rushed into the establishment of Jones & Co.

"We've got him!" Riley exulted. "Caught him at it! Locked him in the vault! And now we'll stand around until the manager gets here and works the combination. He played a smooth game, all right-ask Mr.

Verbeck about it. But we got him! I reckon he's mighty sorry now that he stayed in town to make a fool out of Mr. Verbeck."

They waited, crowding about the place, talking excitedly in whispers, debating whether the Black Star would put up a fight when the door was opened, whether he'd commit suicide and cheat the law, now that he was cornered.

Then the chief came beaming, dreaming of the vindication of his department the newspapers would have to grant. He grasped Verbeck by the hand warmly, patted Muggs on the back, congratulated Detective Riley.

"I didn't tip off the reporters this time," he said. "Too late for 'em, anyway. They'll get it in the noon editions to-day, though. Laugh at the police department, will they? Not after this!"

And then the manager of Jones & Co. arrived, a gentleman the personification of dignity generally, but at present the personification of excitement and dread. He stammered when he talked, and threw up his hands in horror when he saw his establishment crowded with police, and it took the chief some minutes to a.s.sure him that his property was safe and the would-be thief locked in the vault.

He advanced to the door and prepared to work the combination. His nervousness caused him to make a mistake at first, but finally he nodded that all that was necessary to open the door was to turn the handle.

The manager retreated then, to hide behind a show case in fear of flying bullets.

"Might as well come out, Mr. Black Star, and take your medicine!"

Riley cried "We've got twenty men here, with guns pointing at that door. You make a hostile move when we open it, and you'll see your finish!"

He nodded to the police, twisted the handle, and threw the door open.

Light flooded the interior of the vault. Half a dozen officers, Riley at their head, rushed.

A cry of consternation came from the detective. Verbeck and Muggs crowded through to took inside.

On the floor of the vault were empty trays that had held jewels. Among them were empty chamois bags. Mountings of inferior value were scattered about. But no master criminal stood before them, ready for battle, or in token of surrender!

"Gone!" Muggs cried.

"But he can't be gone!" Riley shrieked. "We saw him step into the vault! We came right up, never taking our eyes from the door! Muggs slammed the door and twisted the combination. There's no way in or out except the door!"

"Gone!" Verbeck echoed.

The chief of police swore. The manager of Jones & Co., who had left his place of safety, tore his hair and lamented his loss and berated the police.

"He-he can't be gone!" Riley reiterated.

Verbeck, his heart sinking, stepped inside and looked around. Fastened in the corner of one of the trays was what he had feared he would find-a letter written by the Black Star and addressed to himself. He read it swiftly, then handed it to the chief, and threw wide his hands in a gesture of momentary despair.

And this is what he had read:

Mr. Verbeck and Aids: I am leaving this because I a.s.sume you'll find my other note at the house and follow me here. I dare say that, when you entered you saw me standing before the open door of the vault. You watched, and saw me enter the vault. Did you not? You did not! Your eyes deceived you! I intend waiting here until you arrive, to add one more small bit to my evening's entertainment.

Illusion, my dear Mr. Verbeck-all illusion. The dim light coming in from the street, you know, helps some. You will notice that there are many mirrors scattered around the room. I took the liberty of moving a few of them to serve my purpose. Go back to the door at which you entered and look at the vault. Have your silly Muggs stand ten feet to the right of the door to the room.

Now look at the vault, Mr. Verbeck, and it will appear that the silly Muggs is standing in the vault door. You follow? Simple, old-fashioned mirror illusion that won't even go at country fairs any more. And you fell for that!

For, when you enter the room, I shall be standing within ten feet of you, and you'll imagine you see me in the vault door, and creep forward. I'll take two steps to the right, and you'll think I have entered the vault. You'll advance toward it, and I'll step outside quietly to the window that opens on the court, let myself down a rope already prepared, and be on my way-with this excellent collection of diamonds. All thought out beforehand, you see!

I have made you a laughingstock, as I promised, but I am not done with you yet. I defy you again, Roger Verbeck, as I defy the police. You'll hear from me soon.

They snapped out the lights and tried it-Muggs standing where the Black Star had said-and found it was so.

They went to the court and found an open window from which a rope dangled to the ground floor below.

Then they placed a guard and went out, leaving the manager to estimate and bemoan his loss.

"He's a devil-a devil!" the chief was muttering.

"He's human-and we'll get him yet!" Roger Verbeck answered, and the fighting look was in his face when he spoke.