Early the next morning Jupe made his usual trip to the mailbox at the bottom of the drive. Uncle Titus always got what he jokingly called “junk” mail — notices of sales of scrap metal and other junk he might want to buy for his salvage yard.

Jupe sorted through it until he came to a manila envelope. He could feel something hard and rectangular inside it. It was addressed to Mr. Jupiter Jones and had no address and no stamp. It had been delivered by hand.

He took it back to Headquarters and opened it. Inside the envelope was a tape cassette. Nothing else. No writing on the tape label to explain what it was.

Jupe fitted it into his recorder and hit the play button. He heard only a long silence as the tape unwound. Then finally a male voice spoke clearly and urgently.

“Please don’t come to Mexico,” the voice said. “You’ll be in terrible danger if you do. Please, please, don’t come down here. Stay in California and — ”

The voice suddenly cut off.

That was all. Jupe played the tape to the end. He heard nothing else but silence.

He sat back in his swivel chair. The message was disturbing enough in itself. “You’ll be in terrible danger. ” But something else about it puzzled and worried him. He couldn’t help feeling he’d heard that voice before. It was somehow weirdly familiar.

When Pete drove up next to Headquarters a few minutes later, Jupe asked him to listen to the tape. After explaining where he had found it, he played it straight through.

To Jupiter’s surprise, Pete began smiling. “Is this some kind of joke, Jupe?” he asked.

“A joke?”

“Sending yourself scary messages.”

“I didn’t send it. I told you. I found it in the mailbox.”

“Then someone’s doing a great job of imitating your voice.”

“My voice?”

“Sure.” Pete picked up the recorder. “I’d bet my MG that was you talking on that tape, Jupe.”

Jupiter sat by the window in the battered old bus watching Mexico roll by.

The Three Investigators had originally planned to drive down in Pete’s convertible. But a call to AAA had warned Pete that unleaded gas was hard to find in Mexico. Leaded gas would wreck the MG’s catalytic converter, and Pete would have to get a new one before he could legally drive the car in California again. That would cost at least three hundred dollars.

“No way,” Pete decided. “I’m going to need all my dough to take Kelly out when I get back. So she’ll be glad to see me.”

He had also refused to travel several hundred miles sandwiched in the back of Bob’s VW bug. In the end the three guys had decided to accept Dusty’s suggestion and take advantage of the cheap Mexican bus fares.

Jupe was wearing a new T-shirt. It said hello, I’m friendly in Spanish. He hoped it would encourage strangers to talk to him so he could practice his own fairly good Spanish.

He twisted on the hard plastic seat to look back at the other two Investigators. Bob was reading the paperback history of Mexico he had brought with him. A stunningly pretty Mexican girl had found a place beside him. Naturally. She kept glancing at Bob as though she hoped he’d stop reading and talk to her.

Pete had somehow managed to fit his long legs under the seat in front of him and was fast asleep.

Both of them were wearing new T-shirts too. Bob’s said the survivors, the name of one of the rock groups Sax Sendler handled.

Pete’s T-shirt had Kelly Madigan printed on it. Kelly had given it to him as a going-away present so he wouldn’t forget her. That had surprised Pete. It seemed to mean she wouldn’t forget him either.

Jupe glanced at the woman sitting behind Bob. She didn’t look any different from any of the other Mexican countrywomen on the bus. She was brown-skinned and dressed in a cotton blouse and wool skirt. Two long black pigtails dangled below the purple shawl she wore over her head. Jupe had first noticed her in the bus station in Santa Monica. And although they had already changed buses twice after crossing the border, she was still traveling with them.

Bob had put down his book and was enjoying a talk with the pretty young Mexican girl next to him. He was glad to find she spoke English.

“I’m afraid my Spanish is lousy,” he apologized. “Just buenas dias and stuff like that.”

“How do you like Mexico?” she asked.

“I think it’s great.”

“Why?”

“Well. ” Bob thought about it. “In the States it’s like one of those big bands. Everyone knows their part and has their own sheet music. You can kind of tell what’s coming up next.”

“And in Mexico?” she prompted him with a smile.

“It’s more like a jam session. Everybody taking off and doing their own thing. Not just the way they drive down here. But the way the bus keeps stopping in the middle of nowhere and a bunch of people just disappear into the desert.”

“They’re going to their farms,” she explained. “And they may have to walk five miles from the road.”

“But they don’t seem to mind,” Bob said. “They set off smiling and talking together. Like they were going to their own private party.”

“Maybe you’re right.” She nodded thoughtfully. “I lived for several years in America. Life is much easier there. But people do seem more cheerful in Mexico.”

The bus lurched to a stop in a small town. Jupe glanced at his map, then signaled to Pete and Bob. They had to change buses again, Bob said good-bye to the Mexican girl as he took his tote bag down from the rack. The bus station was a small cafe in a busy street. The three friends hurried into it.

“Boy, am I starved!” Pete exclaimed as they sat down at a table.

Pete and Bob ordered beef burritos with rice and beans. Jupe hesitated. He wasn’t going to be able to stick to his new diet in Mexico. Dusty had warned them not to eat salads or uncooked vegetables on the trip. But rice and beans! That was like begging to put on weight.

He ate two chicken tacos. Chicken was less fatty than beef. And tortillas had less starch in them than bread — he hoped. But the chicken was heavily flavored with chili peppers.

“Argh!” Jupe said as the three guys left the cafe to catch their bus. “My tongue feels like it’s on fire.”

As Jupe walked toward the bus a man in a torn leather jacket suddenly stepped in front of him. He was tall, heavily built, about twenty years old. He put his hand on Jupe’s chest and pushed him back roughly. “No room,” he said in Spanish. “No room for you on this bus.”

The three guys exchanged surprised looks. The Mexicans they had seen so far had seemed so friendly.

Jupe could see half the seats on the bus were still empty. Using his most polite Spanish, he explained this to the Mexican.

The man gave him another, harder push. It felt like a punch in the chest this time.

“No,” he said. “Go away. Get out of here. You and your friends go back to the United States. We don’t want you here.”

“I’m not going back to the United States,” Jupe stated firmly in Spanish. “I’m taking this bus. Please get out of my way.”

Instead of stepping aside, the man in the leather jacket grabbed Jupe by the shoulder and drew him close.

“Get lost,” he said. “Or I’ll beat your brains out.”

Jupe had been practicing his judo particularly hard these past few weeks in his effort to lose weight. He was getting quite good at it. But he didn’t think he was any match for this hefty young Mexican. Before he could get a hold on him, the man would knock out several of his teeth. He quickly freed his shoulder from the other’s grip and stepped back to avoid the blow.

Pete and Bob had been trying to follow the Spanish, but Pete had no trouble understanding exactly what was happening now. He moved up beside Jupe.

“What’s going on?” he asked.

Jupe explained that the man in the leather jacket didn’t want to let them on the bus.