Police headquarters was thrown into a turmoil for the second time that night when the chief received the master criminal's telephone message.

Roger Verbeck and Muggs rushed for the roadster, sprang in, and drove like mad through the streets toward the National Trust Company's building.

The chief shrieked his orders, officers tumbled into department automobiles, and followed Verbeck. They reached their destination, and sprang out. Verbeck already had ascertained that the front doors of the bank were locked and bolted. He rushed around to the alley, followed by Muggs, the chief, and a dozen officers. A detective hurried to telephone Sheriff Kowen.

The basement door was open, and they rushed inside. They found the watchman bound and gagged—he was a member of the Black Star's band, but they needed him again, and so made the attempt to remove all suspicion.

"The Black Star!" he gasped when they had removed the gag and bonds. "He was here with his gang! They carried out gold—went away in autos and——"

Verbeck had rushed on to the vault room. The chief and some of the others followed. They found the door of the vault standing open, money scattered on the floor, papers in confusion.

"He cleaned out all the big stuff!" the chief said. "One of you men telephone the president of the trust company and tell him to hurry down here."

"Here's the letter he mentioned, chief," Verbeck said.

The chief ripped it open and read it, then thrust it into one of his pockets. As he turned away, there was a sharp explosion in the street, then a bedlam of shrieks and cries. They rushed to a window and threw it open.

"Bomb!" somebody in the street was shouting. "It came from the roof!"

"One of that crook's gas bombs!" the chief exclaimed. "On the roof, is he?"

Verbeck already was running toward the stairs, with Muggs just behind him, determined to be in the midst of the affair. Muggs had been complaining again that he was not playing a principal part in this drama, and that he felt he was entitled to one.

Half a dozen officers took after them, the chief bellowed orders and posted guards throughout the bank. He sent other men to the floors above to release the watchmen. And then he followed Roger Verbeck, running up the stairs, puffing and panting, wishing that the elevator was running.

They came to the little steel stairs that led to the trapdoor and the roof. Verbeck tried to open the door, and found that it was fastened on the outside.

"Either the Black Star or some of his men are up there!" Verbeck said. "The door wouldn't be locked on the outside, otherwise."

One of the detectives had procured a fire ax from the hall on the floor below. He ran up the steel stairs and attacked the heavy door vigorously. The chief sent a man for another ax.

More officers had come up the stairs now, and stood at the bottom of the steel steps, waiting for the trapdoor to be opened.

"As soon as we get through, rush up there and go at them," the chief directed. "We don't know how many are up there, so be ready to mix it! Shoot, if you have to, but get him alive if you can. And look out for vapor guns and gas bombs!"

"Somebody on the roof is asking for you, chief!" the man with the ax called down.

The chief hurried up the steps. "Well, who is it?" he demanded.

"This is the Black Star. Can't you recognize my voice? Still practicing violence, I see, and this time on a door!"

"Well, what do you want?" the chief cried. "Do you want to give yourself up?"

"Certainly not, my dear chief. I just wanted to let you know that I was here."

"And we're going to get you!" the chief cried. "If it is necessary we'll get you with a gun! If you start using that vapor stuff when we get the door open, my men will shoot. Understand that? I'll give you one minute to surrender and open the door!"

"Why on earth should I do such a thing as that?" the Black Star wanted to know.

"Because you are at the end of your rope, that's why!" the chief replied. "If you try to go down a fire escape, you'll be plugged. And that's the only way you can get off the roof."

"I have no intention of going down a fire escape," the Black Star replied. "I give you my word of honor—or dishonor, if you prefer it that way—that I shall descend no fire escape to-night. Does that satisfy you?"

"Are you going to give yourself up?"

"Dear me, no! I couldn't think of it. I have had a very pleasant evening, chief—very pleasant indeed—and profitable, also. By the way, did you get your letter?"

An exasperated chief descended the steps and motioned for the detective to go to work with the ax again. The heavy blows began raining against the door. Between them, they could hear the Black Star laughing.

"Get through that door!" the chief shrieked. "We've got him in a trap!"

"I wouldn't be too sure of that," said Roger Verbeck. "He seemed to speak with confidence."

"But how can he get away?"

"The Black Star used to be noted for doing some peculiar and seemingly impossible things," Verbeck reminded the chief.

"I want to be the second man through that door!" Muggs said. "I got it comin' to me, boss. You ain't let me do a thing to-day, and I want to get my hands on that big crook!"

"That's what we all want to do," the chief remarked. "Get ready, men; that door will be open in a minute!"

The detective had succeeded in cutting a hole in it. Now he put his face close to the aperture and looked out. He could see nothing but darkness. Cautiously, he extended a hand and felt for the bolt, located it, shot it back. He whispered the news to those behind him. The officers crowded the steel stairs, and Muggs got well in the van. Muggs declined to be sidetracked longer.

The detective threw the door open, and they stumbled up the steps and to the roof, their weapons held ready, to dart to either side, expecting a shot, or a vapor bomb at least.

Their electric torches flashed, and the roof was bathed in light. There was nothing behind which a person could hide, except two chimneys. The officers approached the chimneys, carefully, ready for instant combat. They circled them—and found nobody.

"He's here—got to be here!" the chief cried.

They rushed to all the fire escapes and found that nobody was on them. They shouted to officers in the street below, and were told that the fire escapes had not been used. They searched every square foot of the roof, looked along the parapet, found nobody.

"I tell you that crook's got to be here!" the chief shouted. "How could he get away?"

"Airplane," one of the detectives suggested.

"Don't be an ass!" the chief shrieked. "An airplane makes a lot of noise. And it wouldn't be easy to pick up a man from a roof in the dark, you fool! The only way it could be done would be to trail a rope and let him grab it, and that would mean a dead man on the pavement below. You ass, an airplane travels with speed!"

"Well, he doesn't seem to be here," Verbeck offered.

"But where could he have gone?" the chief cried. "Even the Black Star can't make himself invisible at will!"

Then they heard the Black Star laugh derisively.

They flashed their torches and again searched the roof. Once more they heard the laugh. Now it seemed to be to one side of them, and now to another. Above them, behind them, in front of them they heard it.

"This thing will drive me crazy!" the chief cried. "Flash those torches again! That crook is somewhere right here on the roof! Look for another trapdoor!"

They searched the roof, and found nothing; but again they heard the laugh, only it sounded far away now. Suddenly the roof was bathed in bright light that seemed to come out of the sky.

"He's up there—on something!" the chief shrieked.

They emptied their revolvers and automatics toward the sky. The light died out, flashed forth again and almost blinded them. Once more they heard the sarcastic laugh of the Black Star, as if far in the distance—and then the light was gone.

They stood silent, looking upward. Not the slightest sound came to their ears, except echoes of the shouts in the street below, where people were wondering about the peculiar, blinding light.

"What does it mean?" the chief cried. "Verbeck, what has that devil done?"

"I haven't the faintest idea," Roger Verbeck replied. "I don't understand that laugh, and I can't imagine where that light comes from. I'd think naturally, that it was an airplane, but, as you said, it would be almost impossible to pick a man off the roof at night—and an airplane makes a lot of noise. And we didn't hear a sound—remember that!"

Once more the voice of the Black Star reached their ears. He seemed to be shouting to them, and to be not so very far away.

"Good night, gentlemen!" he called to them. "It has been a splendid evening of amusement and profit. Good night—and let me express the hope that you'll have pleasant dreams!"

That was all. Though they waited on the roof for half an hour longer, they heard nothing more from him, saw nothing of him, and finally they turned and went back down the stairs, puzzled, angry, but determined to make the master rogue pay.