“I wonder,” said Jupe, “if she really wanted the burro for herself. My hunch is she just didn’t want us to have her.”

“Huh?” Pete said.

But Jupe had no more to say. The guys moved on.

Every evening before sunset Blondie found a place with water and firewood where they could camp for the night. They never saw another human being. Now and then they did see adobe huts with thatched roofs in the distance. But if anyone lived in them, they never showed themselves.

After the second day, Jupe’s legs lost their stiffness. They developed muscles he never knew he had. On the third morning he made a wonderful discovery. His leather belt was too loose for him! He had to take it in a notch.

“It must be all this exercise, riding Blondie,” he told his friends proudly.

That made Pete laugh. “No wonder you’re losing weight,” he said. “No chance for pigging out between meals.”

Jupe didn’t care about the teasing. Whatever the cause, he was thinner. And maybe he had a hope for a date before summer vacation was over. He started to whistle.

That day as they were moving along a ridge the three guys saw a plume of white smoke billow up from beyond a range of mountains ahead. They stopped and watched it.

“That’s all we need,” Bob said. “A forest fire.”

“It’s a long way off,” Pete reassured him. “And maybe if we’re lucky, the wind’ll blow it the other way.”

Jupiter looked thoughtful as they continued on.

That night Dusty arrived in camp an hour after the Three Investigators. He looked worried as he ate.

“I’m going to have to give the horse a day’s rest before it goes lame,” he said when he had finished his meal. “You push on without me. I’ll catch up with you as soon as I can.”

“Sure you can find us?” Pete asked.

“Don’t worry about that. It’ll be easy enough to track you in this kind of country. Two guys on foot and one riding a burro leave a pretty clear trail.”

The next morning after Dusty had divided up the supplies, the Three Investigators set off on their own. Blondie didn’t seem to mind being loaded with the food and the cooking pot as well as their sleeping bags. Jupe joined his friends on foot. They kidded and laughed as they camped that night, relieved to be away from Dusty.

“Let me guess what we’re having,” Bob said to Pete as Jupe made dinner. “Rice and beans?”

“Wrong!” Pete answered. “It’s beans and rice.”

“Actually,” Jupe intoned nasally, “beans a la rice is the selection for this evening. Please prepare your dining utensils.”

After dinner they were sitting around the fire when Blondie suddenly brayed with excitement. They all jumped to their feet, listening.

As usual, they didn’t hear anything until long after Blondie had. Then they caught the sound of footsteps approaching out of the darkness.

A moment later the campfire lit up a large burro slowly ambling toward them. It was obviously much older than Blondie. It wasn’t saddled, but there were several packs roped across its back.

The woman with the black pigtails was walking behind it.

Blondie stopped braying. She seemed delighted to see another of her own kind. She trotted forward and the two animals rubbed noses.

The Mexican woman came closer.

“Don’t worry,” she said in Spanish. “I haven’t come to try to steal your burro this time. I want to talk to you. My name is Mercedes and I know who you all are. But before we talk, please give me something to eat. I’m hungry.”

Jupe gave her a plate of rice and beans. Mercedes sat down by the fire. She obviously was hungry. She didn’t say another word until she had finished.

Jupe had seen her only at a distance on the bus. This was his first chance to study her. He watched her guardedly while she ate.

She was around forty, he guessed. A good-looking woman with a strong, determined face. She was wearing a loose woolen skirt with pockets, Mexican boots, and a blouse with short sleeves. Her skin was deep brown and her eyes were as dark as Ascencion’s. On the whole, he guessed, she would make a good friend and a dangerous enemy.

She put aside her empty plate and glanced at the man’s watch she was wearing. The strap had come loose and the watch had slid down her wrist. She quickly pushed it back into place.

“I don’t have much time,” she said, still in Spanish. “I’ve got to get back to the lake. So I’ll tell you what I have to say as briefly as I can.” She looked at Jupe. “I’m sorry I don’t speak any English. But from what I saw of you on the bus trip, you understand Spanish quite well. No?”

Jupe remembered the Mexican guy in the torn leather jacket who had tried to stop them from getting back on the bus. She had obviously overheard Jupe’s argument with him. And Jupe had seen her pay that man right afterward.

He nodded. “I can understand what you say,” he told Mercedes. “If you speak slowly.”

“Good.” Mercedes drew her feet up, covering them with her skirt. Then for the next fifteen minutes she talked in a low, urgent voice. Jupe had to interrupt only now and then to ask her what a word meant. When she had finished, he felt confident he had understood her whole story.

Mercedes stood up. The Three Investigators got up too. She shook hands with each of them. Then, as suddenly and mysteriously as she had arrived, she led her burro off into the night.

Pete put more wood on the fire. “Okay, what was that all about?” he asked.

“What a story!” Jupe told his friends as they sprawled on the ground. “I’ll run it by you in a minute. But first, Bob, give me the lowdown on Pancho Villa.”

“What do I look like, the Mexican Public Library?” Bob exclaimed.

“Come off it. You’ve been reading that Mexican history book ever since we left Rocky Beach. Did you finish it yet?”

“Yeah.” Bob smiled. “I finished it that day you almost became a historical item yourself by drowning in the lake.”

“Great.” Jupe smiled too. “The part I’m interested in is around 1916. What do you know about Pancho Villa?”

“There was a big revolution going on in Mexico then. Pancho Villa was one of the stars. Some people think he was just an outlaw, like Jesse James. But he managed his own private army. And he won a lot of battles.”

“Did he spend any time up here in the Sierra Madre?”

“Yeah. This was one of his bases. He’d go swinging down into the desert and hold up trains. Then he’d hide out up here.”

Jupe nodded thoughtfully. “At least Mercedes was telling the truth about that,” he said.

“You mean that’s what she was yakking about the whole time?” Pete asked. “About a dead guy called Pancho Villa?”

“No, not the whole time.” Jupe looked at Bob and went on. “But we might be on the trail of that treasure of the Sierra Madre you’re always going on about. Pancho Villa’s loot. Mercedes said he robbed a train one day and got away with thousands and thousands of dollars’ worth of silver pesos. Then he came up here and hid the money in a cave. Unluckily for him, he used the same cave to store his gunpowder in. One of his men got careless and the gunpowder exploded. Part of the mountain collapsed. It buried all those silver pesos under tons of rock and totaled some of Villa’s soldiers. He started to clear away the fallen rock. But then the other side in the revolution attacked him and he had to get out of these mountains fast.”

Jupe paused for a moment.

“Mercedes says the silver’s still there,” he finished.

Pete and Bob were silent while they thought that over.

“How did she get onto all this?” Pete wanted to know.

“She said her grandfather was one of Villa’s soldiers and he passed the story down through the family.”

“What was she saying about Dusty?” Bob asked. “I did catch his name. I made out something about a burro, too.”

“I’m getting to that,” Jupe told him. “She said about three months ago a close friend of hers, a young American named Brit, came out of these mountains. He and his father had been prospecting up here. Looking for Pancho Villa’s cave. And they thought they’d found it. At least Brit told Mercedes they had.”