"Are you sure it's them?" asked Ned.

"Bless my toothpick!" cried Mr. Damon. "It isn't possible, Tom?"

"Yes, it is," said the young inventor. "It's the Fogers all right. Take a look for yourself, Ned."

The other lad did, and confirmed his chum's news, and then Mr. Damon also made sure, by using the glass.

"No doubt of it," the odd man said. "But what are you going to do, Tom?"

Our hero thought for a moment. Then, once more, he looked steadfastly through the glass at the other carts. The occupants of them did not appear to know that they were under observation, and at that distance they could not have made out our friends without a telescope. Tom ascertained that the Fogers were not using one.

"Has Senor Swift any orders?" asked Delazes. "Who are these Fogers? Enemies of yours I take it. Why should they follow you merely to find a ruined city, that the ruins and relics may be studied?"

"Here are the orders," spoke Tom, a bit sharply, not answering the question. "We'll camp and have supper, and then we'll go on and make all the distance we can after dark."

"What, travel at night?" cried the Mexican, as if in horror at the suggestion.

"Yes; why not?" asked Tom calmly. "They can't see us after dark, and if we can strike off on another trail we may throw them off our track. Surely we'll travel after supper."

"But it will be night--dark--we never work after dark," protested Delazes.

"You're going to this time," declared Tom grimly.

"But the oxen--they are not used to it."

"Nothing like getting used to a thing," went on the young inventor. "They won't mind after a rest and a good feed. Besides, there is a moon to-night, and it will be plenty light enough. Tell the men, Senor Delazes."

"But they will protest. It is unheard of, and--"

"Send them to me," said Tom quickly. "There'll be double pay for night work. Send them to me."

"Ah, that is good. Senor Swift. Double pay! I think the men will not object," and with a greedy look in his black eyes the Mexican contractor hastened to tell his men of the change of plans.

Tom took another look at the approaching Fogers. Their carts were slowly crawling up the trail, and as Tom could plainly see them, he made no doubt but that his caravan was also observed by Andy and his father.

"I guess that's the best plan to throw them off," agreed Ned, when they were once more underway. "But how are you going to explain to Delazes, Tom, the reason the Fogers are following us? He'll get suspicious, I'm afraid."

"Let him. I'm not going to explain. He can think what he likes, I can't stop him. More than likely though, that he'll put it down to some crazy whim of us 'Americanos.' I hope he does. We can talk loudly, when he's around, about how we want to get historical relics, and the Fogers are after the same thing. There have been several expeditions down this way from rival colleges or museums after Aztec relics, and he may think we're one of them. For the golden images are historical relics all right," added Tom in a lower voice.

The Mexicans made no objections to continuing on after supper, once they learned of the double pay, and a little later they went into camp. A turn of the trial hid the Fogers from sight, but Tom and his friends had no doubt but what they were still following.

It was rather novel, traveling along by the light of the brilliant moon, and the boys and Mr. Damon thoroughly enjoyed it. Orders had been given to proceed as quietly as possible, for they did not want the Fogers to learn of the night trip.

"They may see us," Tom had said when they were ready to start, "but we've got to take a chance on that. If the trail divides, however, we can lose them."

"It does separate, a little farther on," Delazes had said.

"Good!" cried Tom, "then we'll fool our rival relic hunters and our museum will get the benefit." He said this quite loudly.

"Ah, then you want the relics for a museum?" asked the Mexican contractor quickly.

"Yes, if they pay enough," replied Tom, and he meant it, for he had no doubt that many museums would be glad to get specimens of the golden images.

Just as they were about to start off Tom had swept the moonlit trail with his night-glass, but there was no sign of the Fogers, though they may have seen their rivals start off.

"Let her go!" ordered Tom, and they were once more underway.

It was about five miles to where the trail divided, and it was midnight when they got there, for the going was not easy.

"Now, which way," asked Delazes, as the caravan came to a halt. "To the left or right?"

"Let me see," mused Tom, trying to remember the map the African missionary had sent him. "Do these roads come together farther on?"

"No, but there is a cross trail about twenty miles ahead by which one can get from either of these trails to the other."

"Good!" cried the young inventor. "Then we'll go to the right, and we can make our way back. But wait a minute. Send a couple of carts on the left trail for about two miles. We'll wait here until they come back."

"The senor is pleased to joke," remarked the Mexican quickly.

"I never was more earnest in all my life," replied Tom.

"What's the answer?" asked Ned.

"I want to fool the Fogers. If they see cart tracks on both roads they won't know which one we took. They may hit on the right one first shot, and again, they may go to the left until they come to the place where our two carts turn back. In that case we'll gain a little time."

"Good!" cried Ned. "I might have known you had a good reason, Tom."

"Send on two carts," ordered the young inventor, and now Delazes understood the reason for the strategy. He chuckled as he ordered two of the drivers to start off, and come back after covering a couple of miles.

It was rather dreary waiting there at the fork of the trail, and to beguile the time Tom ordered fires lighted and chocolate made. The men appreciated this, and were ready to start off again when their companions returned.

"There," announced Tom, when they were on the way once more, "I think we've given them something to think over at any rate. Now for a few more miles, and then we'll rest until morning."

All were glad enough when Tom decided to go into camp, and they slept later than usual the next morning. The trail was now of such a character that no one following them could be detected until quite close, so it was useless to worry over what the Fogers might do.

"We'll just make the best time we can, and trust to luck," Tom said.

They traveled on for two days more, and saw nothing of the Fogers. Sometimes they would pass through Mexican villages where they would stop to eat, and Tom would make inquiries about the ancient city of Poltec and the plain of the ruined temple. In every case the Mexicans shook their heads. They had never heard of it. Long before this Tom had ascertained that neither Delazes nor any of his men knew the location of this plain nor had they ever heard of it.

"If there is such a place it must be far in--very far in," the contractor had said. "You will never find it."

"Oh, yes, I will," declared Tom.

But when a week passed, and he was no nearer it than at first even Tom began to get a little doubtful. They made inquiries at every place they stopped, of villagers, of town authorities, and even in some cases of the priests who obligingly went over their ancient church records for them. But there was no trace of the temple plain, and of course none of the city of gold.

Peasants, journeying along the road, parties of travelers, and often little bodies of soldiers were asked about the ruined temple, but always the answer was the same. They had never heard of it, nor of the head-hunters either.

"Well, I'm glad of the last," said Mr. Damon, looking apprehensively around, while Eradicate of his head to see if it was still fast on his shoulders.

It was a weary search, and when two weeks had passed even Tom had to admit that it was not as easy as it had seemed at first. As for the Mexicans, they kept on, spurred by the offer of good wages. Delazes watched Tom narrowly, for a sign or hint of what the party was really after, but the young inventor and his friends guarded their secret well.

"But I'm not going to give up!" cried Tom. "Our map may be wrong, and likely it is, but I'm sure we're near the spot, and I'm going to keep on. If we don't get some hint of it in a few days, though, I'll establish a camp, go up in the air and see what I can pick out from the balloon."

"That's the stuff!" cried Ned. "It will be a relief from these rough ox carts."

So for the next few days they doubled and redoubled on their trail, criss-crossing back and forth, ever hoping to get some trace of the temple, which was near the entrance to the city of gold. In all that time nothing was seen of the Fogers.

"We'll try the balloon to-morrow," decided Tom, as they went into camp one night after a weary day. Every one was tired enough to sleep soundly under the tents which were set up over the carts, in which beds were laid. It must have been about midnight when Tom, who felt a bit chilly (for the nights were cool in spite of the heat of the day), got up to look at the campfire. It was almost out so he went over to throw on some more logs.

As he did so he heard a noise as if something or somebody had leaped down out of a tree to the ground. A moment later, before he could toss on the sticks he had caught up, Tom was aware of two eyes of greenish brightness staring at him in the glow of the dying fire, and not ten feet away.