feet. He was leering.

Blake watched the remaining guards from the corner of his eye. O'Toole was still standing quietly by the door, alert and ready. He saw Blake's eye on his, and winked deliberately. O'Toole, Blake decided, was ready any time.

"You were right on the murder angle," Harror admitted. "Pretty smart, ain't you?"

"About some things," Blake admitted. "I don't fall for everything I read in the papers. I know you used a hidden mono track to get us here, and that you'll probably send us back over it into a nice deep canyon, when you have everything you want off the train."

Harror leaned over silently and spat into his face. Blake saw red. With a lightning thrust he smashed the lamp from the table and plunged the room into blackness. From O'Toole's side of the room a ray gun belched fire, but Blake was already out of range. He heard a cry of pain and realized that Harror had caught the flame on the arm. Harror, outlined in the light of the ray was almost on top of him.

From the spot where O'Toole had been, Blake heard a sullen thud and a long groan of pain. Dodging from Harror's plunging fall, Blake knew O'Toole was doing his part. He grasped the edge of the table and tried to thrust it in front of Harror. The man swore loudly and kicked it away. There was a slit of light coming from under the door.

In its path, Blake saw Harror standing above him, a hairy fist descending like a ton of lead. He twisted his face around, sensed Harror's blow miss him by a fraction of an inch. Diving low he hit Harror a body blow with his shoulder and the giant doubled in pain. Blake swung upward before Harror could regain his balance, and set his fist crashing into Harror's face. The giant swung backward like an enraged elephant. Two more flashes of electro-fire went spurting over his head and O'Toole started to sing in a loud, off-key voice.

"Slug 'em," O'Toole chanted. "It's the Irish that are in this mess tonight."

In the darkness, Blake grinned painfully. His lip was split and bleeding. His arm ached from the forceful contact with Harror's jaw.

Another guard went down in the scuffle and O'Toole howled his battle cry again.

Harror was silent. Blake changed his position wearily, waiting for some sign. He heard Harror breathing loudly from the far corner. The blow on the face must have dazed him.

Blake closed it slowly, listening to Harror. Waiting for him to strike again. Then two giant arms closed tightly around his chest, cutting off his breath. He tried to shout, but his lips made no sound. He felt himself sinking toward the floor, Harror on top of him. Harror was holding on with all his strength.

Blake relaxed slowly, and his head fell to one side. He felt the grip relax just a trifle, and gathered all his remaining strength. With a terrific uppercut, Blake's arm shot upward, catching Harror squarely on the chin. There was a sudden snap as the giant's head tipped back as though unhinged. His arms relaxed and Blake fell away from him.

The Irishman had done his job well. The room was quiet.

Then: "Jeff, Jeff, are you all right."

Blake chuckled.

"I've got condensed ribs," he said. "But I think Harror will lie still for a while."

"Golly!" O'Toole sighed in relief. "You sure had a Goliath on your hands. Wish I could have helped you."

"What became of those two guards," Jeff asked? "Seems to me they had you on the spot for a while."

"Aw!" O'Toole said. "I got hold of one of them fire guns and there wasn't anything to it."

Blake had reached the door to the outer cavern. He opened it a couple of inches and looked out. The Silver Mask gang were still working on Mono 6.

Even as he watched, a man detached himself from the gang at the far end of the train and came slowly toward the partially opened door. Blake jumped back and closed it tightly.

"Get two of these guards out of their uniforms," he said. "Make it quick. We've got more trouble coming."

A quick knock came on the door. Blake said, in a hard voice.

"Yeah! Who is it?"

"Slater," was the reply. "Tell the boss we got the train cleaned out. We're all ready to set it loose."

In the light of the open door, Blake looked at O'Toole. The Irishman was already in one of the Silver Mask uniforms. His face was hidden and he looked like one of the gang.

"Tell him the boss will be all set in a minute," Blake said. "I've got to get into one of these outfits."

O'Toole flung the door open wider and pushed the bodies of the silent guards out of sight.

"We'll be out in a minute," he said to Slater. "Get her ready to roll."

"Yes sir," Slater answered him respectfully. "The cab is all fixed, and the motors are turning. The hidden door has been opened so we better make it snappy."

O'Toole nodded.

"Okay," he said. "Make sure you don't leave anything on board that's useful. And Slater...."

The man had turned. Now he hesitated and turned back.

"Yeah?"

"Harror is staying here," O'Toole said quickly. "He ain't feeling so good. Says I'm to give the orders."

Slater laughed.

"That's a good one," he chuckled. "How long since that gorilla started giving orders around here."

Still laughing, he turned and went back toward the waiting masked men.

O'Toole closed the door and ripped the mask away.

"This is it," he said quickly. "I knew Wade was mixed up in this business. Harror isn't the real boss here."

Blake was half way into a uniform of the Silver Masks. He finished his job before answering. Then he spoke.

"I know you and Ferrell hate Wade's guts," he said slowly, "but...."

"It's not me so much," O'Toole protested. "Ferrell said long ago that Wade was in this mess. He didn't seem to get any action on the case. Now with the guy Slater saying Harror isn't the boss, there isn't any other answer."

"Sorry, O'Toole," Blake said. "I should be willing to admit that Wade's our man. I don't know why I can't. It's just that blood is pretty thick stuff, I guess. It's hard to think your own brother would turn on you like this."

O'Toole lowered his head.

"We've got to do something," he said quietly. "Those guys won't sit out there waiting forever."

Blake stood up slowly.

"Supposing Wade isn't the chief," he asked. "What then?"

"They'll kill us all, just as they already plan to," O'Toole groaned. "We might as well take a flying chance."

Blake shook his head.

"I've got a better idea," he said.

"Then spill it. We haven't much time."

"To begin with," Blake said. "If Wade was in this he'd have shown up here long ago. The paper said he couldn't be located. I'd recognize my twin even in one of these outfits."

O'Toole protested.

"Then who is the chief? He's here somewhere and Slater sure didn't intend to take orders from Harror."

"He must be on the train," Blake answered.

"Now you're crazy," O'Toole answered savagely. "The people on Mono 6 have been locked up for hours. If the leader of the Silver Masks was among them he'd have taken charge hours ago."

"Unless," Blake said thoughtfully, "he didn't want any of us to know he was the leader."

O'Toole pulled the mask down over his eyes.

"Let's get out of here," he said. "You've got something up your sleeve and I'll play the cards the way you want them."

"One more thing," Blake told him. "These men had to have a track to get Mono 6 into this cave. When it goes out again we'll be on the same track, but it will end in a canyon or deep lake."

"Go on."

"Well! We've got to get started on that trip. After we are out you and I will have to take our chances of stopping the mono."

"And I thought Grudge Harror was a tough baby," O'Toole grinned.

"It isn't a matter of being tough," Blake said. "Can you handle the engine room alone?"

"Handled it for years," O'Toole said coolly. "But I'd