A half a dozen policemen were on guard outside the museum. They walked around the building continually, and communicated at the end of each hour with one of the guards inside. Now and then they gathered near the entrance to talk and wish their vigil was over.

Ten minutes after the Black Star's man had flashed his torch from the window, these six officers were startled by sounds of an altercation in the street. Two men, their voices raised, were quarreling. Others passing in the street stopped to listen. Threats were hurled back and forth. The men grappled, started to fight.

Two of the policemen left the museum and started running toward the combatants. When they were halfway one of the fighting men darted backward, drew a revolver and began firing.

There was a crowd on the corner now. The quarrelsome one continued to shoot; the other man fell in the street.

The four other policemen forgot the museum. They ran toward the corner, clubs in their hands, to beat back the crowd, to help take charge of the murderer, to send for an ambulance, if it proved to be necessary.

The Black Star's man observed this from a window. He flashed his torch again, and then ran down the stairs and to a little side door of the museum, which he unlocked.

Four men darted across the street and through this door. It was locked again immediately.

"All of them down and out!" the man who had been inside reported. "We'll have to work swiftly. They'll be expecting a guard to show his face at the door at the end of the hour. Come with me—I know the paintings the boss wants."

"How about that electric current?" one asked.

"I turned it off, of course. Hurry!"

They ran up the stairs and into one of the galleries. The man who had been inside indicated six paintings. Men crawled beneath the protecting railings, drew knives and started cutting the paintings from their frames.

"No time to waste!" the leader informed them. "We've got about fifteen minutes more."

He ran to one of the windows and glanced out at the street. The crowd was growing larger. The police had ascertained that the man who had fallen was not shot, but had stumbled in his mad haste to get away. The two men had been arrested, and the patrol auto called. None of the police had started back toward the museum, though some of them glanced in that direction now and then.

Inside, the paintings had been cut from their frames and made into rolls. The rolls were tied up with rope and then lashed together.

"Out you go!" said the man who had hidden inside.

They hurried down the stairs and to the little side door. The one ahead opened it and glanced out.

"Coast all clear!" he announced.

Two went first, carrying the roll of paintings with them. The others left one by one, darted across the street, and each went in a different direction. Those with the paintings had an automobile waiting; they jumped in and were driven rapidly away.

The men who had fought were carried away to jail; their part had been done well. The policemen went back to the museum, joking about the fight they had witnessed.

"They'll make it up in the morning and get fined for fighting and discharging firearms," one of them declared. "Business quarrel, eh? Pretty vigorous business men, I think!"

"Suppose everything's all right inside?" another asked.

"That gang inside is so busy playing cards that they wouldn't know it if a battle was staged in the street."

The end of the hour came, but no guard showed himself at the front door to say that everything was all right. One of the policemen pounded upon it, but got no response.

"That's funny!" he said. "They ought to answer—that's their orders!"

He pounded upon the door again, and still he got no reply from those inside.

"Think we'd better go in?" one of the others asked.

"We've got orders not to do it unless we know there's trouble inside."

"Well, there may be trouble."

"Card game—that's all. You listen to me—hand that guard a call down when he shows up. He's a sort of fresh guy, anyway—thinks he owns the museum, I guess!"

Once more he pounded on the door and got no response. The police began to look serious.

"Aw, how could anything happen?" one of them asked. "Nobody could get into the museum, could they? And there was nobody in there when it was locked up except them that belonged. Ain't we been on watch?"

"Well, that scrap called all of us across the street for a time, remember."

"Yes, and we'd better forget that if there happens to be any trouble inside. I think we'd better go in and investigate. This doesn't look exactly good to me."

He took a key from his pocket—a key to the front door of the museum, that had been given him for just such an emergency. He unlocked the door and went in with two of the others, locking the door behind him.

They hurried through the entrance and started down the corridor toward the wide stairs that led to the floor above. The one in advance gave a cry of horror and started forward. Stretched on the marble floor were policemen and museum guards, unconscious, and plainly drugged in some manner.

"Call headquarters!" one of the policemen shrieked. "Get the chief!"

Another ran to the nearest telephone, which happened to be in the office of the custodian. Within a short time he had the chief on the wire.

"This is Officer Riley, at the museum," he said. "There's something wrong here. No guard showed up at the front door at the end of the hour, and so we came inside. We found all the guards and officers unconscious, laid out!"

"What's that?" the chief cried. "What laid 'em out? What's happened out there?"

"We just got inside the building—haven't had time to investigate—don't know what's been going on!" Officer Riley gasped. "Thought I'd better call you at once."

"Keep your eyes open—we'll be right up there!" the chief cried. "Keep right on the job!"

"Better bring the police surgeon with you, chief. There seems to be something wrong with these men."

That telephone conversation caused another tumult at police headquarters. The chief bellowed his orders, then ran with Verbeck and Muggs to the former's roadster, which was in readiness at the curb. With Verbeck at the wheel, the powerful car dashed through the streets toward the museum, and behind it came half a dozen police department autos filled with detectives.

They reached the museum, left the cars and hurried to the entrance. One of the men inside unlocked and opened the door.

"They are still unconscious, chief!" he reported. "Looks to me as if they had been doped."

The police surgeon made a swift examination.

"They have been drugged," he announced, "and pretty badly, at that. I'll have to get busy on them at once, or we'll have dead men on our hands."

"Bring them around as soon as you can," the chief said. "I want to hear what they've got to say. And you men search the entire building! We'll look into this! One of you call up the superintendent of the museum and get him down here. Lively!"

The officers scattered throughout the big building, turned on all the lights, and began their search. They found the unconscious guards on the upper floor and carried them below for the police surgeon to work on. The surgeon sent in a call for his assistants.

Policemen who searched the statuary hall discovered the open trapdoor. They got up into the attic, and investigated there, and found nothing except dust and footprints in it. Down to the first floor they went to report this.

Verbeck and Muggs hurried to the attic and investigated for themselves.

"Very simple," Verbeck said. "Some member or members of the gang got up here during the day, remained in hiding until night, and then got down and handled the guards and officers."

"Yeah, but where are they now?" Muggs wanted to know.

"Not in the building, you may be sure. They managed to get out in some manner."

"And what did they swipe?"

"The superintendent will have to tell that, I suppose. There are several thousand things in this place, Muggs, that are almost priceless. The Black Star has done it again. Let's go downstairs and see if there is anything in the nature of a clew."

They hurried down the stairs. The superintendent of the museum had just arrived—a worried, frantic superintendent who immediately telephoned for more guards and one of his assistants.

"I am almost afraid to look," he announced. "Do you suppose anything has been taken?"

"That little side door is unlocked," one of the detectives reported to the chief.

"It shouldn't be," said the superintendent. "It always is locked except when we are receiving new exhibits, which are delivered at that entrance."

Verbeck grasped one of the officers by the arm.

"Have you watched closely all night?" he demanded.

"Yes, sir."

"Didn't leave the museum at all?"

"For a few minutes. There was a shooting scrape at the corner——"

"Did all of you go there? How long were you gone? Speak quickly, man!"

"Weren't gone more than half an hour. But we watched the museum, just the same. It's light——"

"From the corner you couldn't see that little side door!" Verbeck thundered. "Any of the Black Star's men who had hidden in the museum could have rendered these guards and officers unconscious, taken what they wished, and walked right out of that side door with it, while you were over at the corner. That fight was staged for a certain purpose!"

"Oh, you fools!" the chief cried. "The newspapers are right—the police force is a gang of imbeciles! Idiots! You've let him get away with it again!"

The superintendent of the museum had been going through the building with a couple of detectives, and now they heard his cry of surprise and rage from the upper floor.

"What is it? Find something missing?" the chief cried.

"Six famous paintings!" the superintendent shrieked. "Six of them gone! Six priceless masterpieces—cut from their frames—carried away! The protective current—it must have been turned off! Six of the most priceless pictures!"

"Great Scott!" the chief ejaculated.

"Now there will be a fine row!" Verbeck said. "We've got to catch the Black Star and get those paintings back! Every art lover will howl until we do! And, worst of all, they didn't belong to the museum—they were merely loaned. And the six are worth more than a million dollars!"