Sambo groaned; Nicolas grinned.

"All right," Tom Reade laughed. "I'll be back as soon as I can."

Away he raced at a dog-trot, chuckling. The contrast between bulky Sambo and little Nicolas and the big negro's comic fear of the slim little fellow kept Reade laughing.

"But where on earth did Nicolas learn that trick?" Tom wondered. "I shall have to get him to show it to me. Plainly that trick is worth more than all the muscle that I spent so many years in piling on."

Tom headed his course for the sh.o.r.e end of the wall. Here he would find men in abundance. Moreover, now that the big black was a prisoner the men would hardly be needed on the wall.

"I think I know just how Sambo worked it, too," the engineer reflected, as he ran. "He swam out into the Gulf, towing that little scow behind him.

Neither his black head nor the little scow would be seen far on the water on a dark night. Sambo, when he got near enough, could take one of the metal tubes, swim in under water to some point where no watchman was near, and stick the tube fast into the wall. Then another tube, and another---all under water where they would not show to a pa.s.sing watchman.

"Then, when he had all in place, and while no patrolling watchman was too near, Sambo could begin to attach the wires. That would take but a few minutes. Whenever any one came too near Sambo had but to swim out a little way and tread water until he could return to his job. When, at last, all was complete, Sambo would attach a wire from the bombs to a wire moored at a stated point under water, and then swim in, work his magneto, and touch the whole thing off from a safe hiding place on sh.o.r.e. The explosion itself would shatter the last length of wire. Oh, but it was all slick and easy!"

Not increasing his speed, but keeping steadily at the jog-trot, Tom was at last near enough to the wall to raise his voice and shout.

"Hullo!" came back the answer.

"This is Reade, the chief engineer," Tom answered, through the night.

"We've caught the fellow that has been blowing up the wall. A half a dozen of you men hurry over here with your lanterns. Come on the run."

The man who had answered summoned several of his comrades as quickly as he could. As the men had to come in from the wall, however, it took a little time. Then six men reported, almost breathless, to Reade. Still behind them came Corbett on the run, summoned from the boat.

"What's this I hear, Mr. Reade?" puffed the foreman. "You've solved the mystery and caught the fellow who has been dynamiting the wall?"

"Got him and he's tied up, waiting for his ride to jail," Tom chuckled.

"How did it happen, sir?" asked Corbett, staring with his eyes very wide open.

"I caught the fellow---a huge giant of a negro, the same fellow who got Hazelton the other night," replied Tom. "But before the fight was over the black 'got' me, instead, and had me tied up. Then Nicolas came along and put the negro out of the fight, and---"

"Nicolas?" demanded Foreman Corbett incredulously.

"Yes. Nicolas proved himself to be the most fiery little bunch of fighting material that I have ever seen," laughed Reade, as they walked rapidly along.

"How could that Mexican wallop a giant?"

"I'll ask Nicolas to show you, to-morrow," Tom laughed mischievously.

"But, Corbett, I believe that four bombs are even now attached to some part of the retaining wall, ready to be set off.

"Great Scott!"

"They won't be set off, though," continued Reade. "I found the firing magneto, and had a chance to cut the wires."

The foreman wanted to ask more questions, while the half dozen workmen trudged along close at their heels, eager to hear every word. Tom, however, suggested that they save their breath in the interest of speed, until they had Mr. Sambo Ebony in safe custody.

"Here we come, Nicolas!" Tom called, as the party neared the spot where captor and captive had been left.

There was no response.

"Nicolas!" Tom called again, with a start.

Still no answer.

"I don't like the look of that," Reade uttered. "Let's get there on the sprint!"

Tom himself caught at one of the lanterns, leading the way. Neither the negro nor the Mexican was where the young chief engineer had left them.

Feverishly, Tom began to search the ground, holding his lantern close.

"Hang the luck!" he quivered, pointing to fragments of cord on the sand.

"That negro simply burst his bonds---and now where is he? Where is Nicolas, for that matter? I thought the little fellow, with his trick, could easily take care of the big black."

But, though they spread out and searched, there was no sign of either the negro or the little brown man.

"I can't understand what has happened," quivered Tom Reade, thinking more of the staunch little Mexican than of the loss of the prisoner.

CHAPTER XVI

A TEST OF REAL NERVE

"What an idiot I was not to stop to consider that Sambo Ebony could snap those cords!" groaned Tom, staring disconcertedly about him. "Yet, if Nicolas were safe I wouldn't so much mind the escape of the black. I shall see him again, and I shall know him wherever I see him."

"Let's look for the trail," proposed Foreman Corbett, holding one of the lanterns close to the ground.

The trail, however, was easy neither to distinguish nor to follow.

"We may as well leave here and search farther," concluded the young engineer. "Before we go, though, we'll get the magneto and take it with us."

Then the procession turned toward the land end of the retaining wall.

"If Nicolas doesn't show up soon," Tom murmured to the foreman, "I shall notify the Blixton police and offer a reward for news of him. That little fellow is too faithful to be left to his fate."

"What would the negro want of Nicolas?" queried the foreman.

"Revenge," Tom replied. "It makes a big bully like him furious to be handled the way Nicolas treated him. But I can't understand how Nicolas failed to repeat his clever trick with the black."

Arrived at the water front the magneto was dumped into the motor boat.

"Seems to me I would smash that thing all to pieces," Suggested Foreman Corbett. "It has done harm enough around this wall."

"I don't believe in destroying anything that is useful," Reade answered, shaking his head. "Besides, we are going to capture Sambo yet, and then we shall want that magneto for evidence."

"What are you going to do to find Nicolas?" Corbett wanted to know.