CHAPTER XXIII.

BOB IS KIDNAPPED.

For a minute or two the unexpected encounter so astonished all concerned that no one spoke. Noddy seemed ill at ease from meeting his former acquaintances, but Vasco Bilette smiled in an evil way. Chance had thrown in his path the very person he wanted. Tom Dalsett was the first to speak.

"Well, we meet again," he said, with an attempt at cheerfulness. "How do you all do?"

"I don't know that we're any the better for seeing you," remarked Professor Snodgrass, who was plain-spoken at times.

"Oh, but I assure you it's a sight for sore eyes to get a glimpse of you once more," went on Tom. "Besides, this is a free city, you know, even if it is an old, underground one; and we have as much right here as you have."

"True enough," broke in Jerry. "But you may as well know, first as last, that we're done fooling with you and your gang, Noddy Nixon. If you annoy us again there's going to be trouble!"

Noddy did not reply. He seemed anxious to get away, but Dalsett and Vasco urged him to stay, and they had secured quite an influence over the youth.

"We must have come in by the same passage you did," went on Dalsett. "You left it open behind you. We were wandering around in the dark tunnel until we discovered this door a little while ago. Lucky, wasn't it?"

"For you chaps, yes," commented Ned.

"Some of us were nearly killed in the tumble," went on Dalsett. "We got out of it rather well, on the whole."

"You'd better come inside and have nothing more to say to him," said the professor to his friends. "This spoils all our plans."

"Never mind; perhaps we can give them the slip among the ruins," said Jerry.

He went back into the ancient temple, and the others followed him. Noddy continued to stare as if he thought the whole thing was a dream. As for Vasco and Dalsett, they were much pleased with the turn affairs had taken.

But the Mexicans were excited. Several of them had been bruised by the fall into the tunnel, and they wanted to proceed at once and kidnap Bob, so they could get the ransom money. But Vasco would not permit this. He did not believe in using force when he could use stealth. Besides, he was a coward, and afraid of getting hurt, if it came to a fight.

"Let them go," he said to his men, who murmured as they saw their prospective captive and his friends retreat into the temple. "Let them go. They can't get away from here without letting us know. We are better off than before. We can capture the fat boy whenever we want to now."

With that, Vasco's followers had to be content. As Dalsett had said, Noddy and his cronies, after groping about in the dark tunnel for some time, had finally discovered the door by which the boys and the professor had entered the ancient city. They had pushed it open and come face to face with our friends.

"Bah!" exclaimed one of the Mexicans. "It is always to-morrow and to-morrow in this business. Let us fight them! Let us get the captive and let us share the ransom."

"We'll do the trick to-night, sure," promised Vasco. "To-night, positively, we will kidnap Bob."

Meanwhile, all unconscious of the fate in store for him, Bob was making a substantial meal, for the travelers had begun to get dinner after withdrawing from the front of the temple. They talked of little save the appearance of Noddy and his followers.

"How do you suppose he ever got here?" asked Bob.

"Simply followed us," said Jerry. "We left a plain enough trail. Besides, automobiles are scarce in Mexico, and any one seeing ours pass by would easily remember it and tell whoever came along afterward, making inquiries."

"What had we better do?" asked Ned. "Stay here or go away?"

"There'll be more or less trouble if we stay," was Jerry's opinion. "Supposing we go away for a while and come back. If Noddy is after us we may give him the slip and return."

"How are we going to get out of this place?" asked Bob. "We can't go back through the tunnel we came in, as they are now on guard there."

"There must be more than one entrance to this city," spoke the professor. "I think I'll go and hunt for another. When we find it we can take the automobile with us and escape to-night. I wish to be the first person to announce this discovery to the world."

"That's the idea!" exclaimed Ned. "I'll go along to help hunt for another passage, while Bob and Jerry can stay on guard."

"In the meanwhile I'm going to have my swim," said Bob. He went into the tank-room, and immediately uttered a cry.

"What's the matter?" called Jerry.

"The water has all run out," replied Bob, "and there's a big hole here!"

The others came in on the run. They saw that the swimming-pool was empty. Only a little water remained on the bottom in small puddles. They also saw that the pool was made with an incline of stone leading from the floor level down to the bottom. In the side opposite from where the incline was a big black hole showed itself. When the water was at the normal level this hole was invisible. Once the water had lowered it was plain to see.

"What made the water go out?" asked Bob.

"Probably a gate at the end of the tunnel leading from the tank was opened," replied the naturalist. "Or it may be an automatic arrangement, so that when the tank gets filled up to a certain height the water shuts itself off. So we'll defer our bath until the water rises. Perhaps the tides may have some effect on it. We can only wait and see."

"That tunnel is big enough to drive our auto through," observed Bob.

A sudden thought came to Jerry. He whispered to the professor.

"Of course it could be done," replied the scientist after consideration, "but there is the danger of the water rising suddenly while we are in the tunnel. Jerry talks of escaping by means of this new shaft," went on the professor. "We could run the auto down the incline and so out. But we must investigate the place."

The naturalist walked down the incline. Straight in front of them, as they neared it, yawned the black mouth of the passage. The professor would not let the boys come in until he had made an investigation.

He walked quite a distance down the shaft and returned. He seemed in deep thought.

"It will be safe to use the tunnel," he said. "It appears that the water was siphoned out. There is another tank or reservoir connected with this one. They both seem to be fed by springs. When the other tank, which is below the level and to one side, gets full of water, the fluid is siphoned out. As that tank is connected with the one we used, by a pipe, as soon as the water goes out of the first tank, that in the second follows to keep the first tank filled. And so it goes on, from day to day, repeating the operation once every twenty-four hours, I would judge. So we have plenty of time. The tunnel leads to one like that by which we entered the city. I have no doubt but that we can escape through it."

If the professor and the boys could at this time have seen two evil faces peering down at them from a high balcony, they might not have felt so comfortable. San Lucia and Murado were on the lookout, and every move the travelers made was watched.

It was decided to make the escape that night. Accordingly, after supper, the automobile was prepared for a long trip. Things were packed in it, and the professor took along his beloved specimens.

"How are we going to get the car down the incline?" asked Bob.

"I can take it down, all right," replied Jerry.

At length all was in readiness. Jerry and Ned took the front seat, Bob cranked up the car, which was still inside the old temple, and then joined the professor on the rear seat.

"All ready?" asked Jerry.

"All ready," replied Bob.

"Yes, and we are ready, too!" came in a whisper from the ruined doorway of the temple, where Vasco Bilette and his men were in hiding, watching the flight of the travelers.

The Mexican had guessed some sort of an attempt to escape would be made, and was on hand to frustrate it. But the preparations made for taking the auto down into the empty water pool puzzled Vasco. So he was on the alert.

"Here we go!" called Jerry, softly. The auto was vibrating, but almost noiselessly, for the explosions of the motor could scarcely be heard.

Down the incline Jerry took the heavy car, without a mishap. Straight for the open mouth of the tunnel he steered it. It was as dark as pitch now, but the lamps on the car gave good illumination.

"Come on, we have them now!" cried Vasco to his followers. "The boy is in the back seat!"

The Mexicans ran down the incline. By this time the machine was well into the mouth of the shaft. Hearing footsteps behind him, resounding on the stone pavement, Jerry shut off the power for a moment. As he did so the car was surrounded by ugly-looking brigands, who had run up at a signal from Vasco.

"Quick! Grab him!" cried Dalsett.

"I have him!" replied Vasco.

He reached up, and, though Bob was a heavy lad, the Mexican, with the help of Dalsett, pulled him over the rear seat. Bob fought, kicked and struggled. It was of no avail. Then a sack was quickly thrown over his head, and the men ran back out of the tunnel and up the incline, bearing Chunky with them.

"Bob's been kidnapped!" shouted the professor. "Turn the auto around, Jerry, and chase after them!"