SOME DAYS LATER, The Three Investigators were meeting in their headquarters, a converted trailer hidden behind towering piles of lumber and scrap iron in The Jones Salvage Yard. Bob had just read a letter that had arrived that morning from a woman in Malibu Beach who wanted them to find her missing dog when the telephone rang.

Their private phone, paid for by their earnings from odd jobs around the salvage yard, didn’t ring often. When it did, it always promised excitement. Jupiter grabbed it.

“Hello,” he said. “Three Investigators, Jupiter Jones speaking.”

“Hi, Jupe.” The hearty voice of Alfred Hitchcock blared into the office from the loudspeaker Jupe had hooked up. The famous mystery novelist had taken a real interest in the boys. He introduced their cases for them and from time to time found new mysteries for them to solve.

“I’m glad I caught you in,” Mr. Hitchcock went on. “I wanted to let you know that you’ll soon have a visitor.”

“A visitor?” Jupiter repeated. “Is this in reference to a new case?” His eyes sparkled.

“No hints,” said the writer. “I’ve promised not to tell you anything beforehand. I did have a long talk with your visitor and gave you an excellent recommendation. All I can tell you is that you’re about to get a surprising invitation. I just wanted to warn you. Got to go now. Good-bye.”

He hung up, and so did Jupiter. The three boys stared at each other.

“Do you think it’s another case?” Bob asked.

They had no time to speculate, for at that moment the voice of Mathilda Jones, Jupiter’s aunt, came booming in through Headquarters’ open skylight.

“Jupiter! Out front! You have a caller.”

A moment later the boys were scrambling out through Tunnel Two, the big pipe that led from beneath the trailer to a hidden entrance in the workshop section of the yard.

From there it took them only a moment to thread their way around piles of junk to the office.

A small car was parked there, and a young man stood beside it. It was the American who had been part of Prince Djaro’s escort the day they had almost collided with the foreign boy’s car.

“Hello,” he said. “I don’t suppose you expected to see me again. This time let me introduce myself. I’m Bert Young, and here are my credentials.”

He showed them an official-looking card, then slipped it back into his wallet.

“U.S. Government, official business,” he said. “Where can we talk in complete privacy?”

“Back here,” Jupiter said, his eyes bulging a bit. A government agent and he wanted to talk to them in privacy. Also, he had apparently been asking Mr. Hitchcock about them. What did it mean?

Jupiter led the way to the workshop section and found two old chairs. Pete and Bob sat on a crate.

“Maybe you’ve guessed why I’m here,” Bert Young said. They hadn’t, but they waited. “It’s about Prince Djaro of Varania.”

“Prince Djaro!” Bob exclaimed. “How is he?”

“He’s fine and he sends his regards,” Bert Young said. “I was talking to him just a couple of days ago. The point is, he wants the three of you to come visit him and stay for his coronation in two weeks.”

“Wow!” Pete said. “Go all the way to Europe? Are you sure he wants us?”

“You and nobody else,” Bert Young said. “Seems he felt you became real friends that day you all went to Disneyland. He doesn’t have many friends. Among the boys in Varania, he can’t tell who’s really his friend and who’s just buttering him up because he’s the prince. But he’s sure of you. He’d like some friends to be with him, so he’s invited you. I’ll tell you the truth — I helped give him the idea.”

“You did?” Bob asked. “Why?”

“Well,” Bert Young replied, “it’s like this. Varania is a peaceful country. It’s neutral, like Switzerland. We, the United States, like it that way. That means Varania doesn’t give any aid to unfriendly countries.”

“What aid could a small nation like Varania give anyone?” Jupiter asked, speaking at last.

“You’d be surprised. It could allow itself to be a center of spy operations, for one thing. But I can’t go into that. The question is, will you accept the Prince’s invitation?”

The boys blinked. They certainly wanted to go. But there were some problems. Their families, for one thing. And the expense, for another. Not to mention passports. Bert Young disposed of these quickly.

“I’ll talk to your families,” he said. “I think I can convince them that you’ll be in good hands. First of all, I’ll be there, and I’ll keep an eye on you. And you’ll be guests of the prince. Secondly, the government will pay for your plane tickets, clear your passports, and give you spending money. We want you to act like typical American tourists — at least, as the Varanians imagine them. That means buying souvenirs and taking pictures.”

Bob and Pete were too elated at this news to wonder at it. Jupiter, however, frowned.

“Why should the U.S. Government do all this?” he asked. “Not just to be generous. Governments aren’t generous in that way.”

“Alfred Hitchcock said you were smart.” Bert Young grinned. “And I’m glad to see he was right. The truth is, guys, that the government wants you to act as junior agents while you’re in Varania.”

“You mean spy on Prince Djaro?” Pete asked indignantly.

Bert Young shook his head. “Absolutely not. But keep your eyes open. Watch everything that happens, and if you see or hear anything suspicious, report it immediately. The point is, something is stirring in Varania. We don’t know what, and we think you can help us find out.”

“That seems strange,” Jupiter said, looking grave. “I thought the government had sources of information that — ”

“We’re only human,” Bert Young protested. “And Varania is a difficult place to uncover information. You see, the Varanians are a very proud people. They don’t want help from any outside country. And they’re insulted if you offer it. They value their neutrality very highly. Just the same, we’ve been hearing rumors that something is up. I must ask you to keep this strictly confidential.”

Bert Young looked in turn at each of the boys, who nodded seriously.

“Good. Then I’ll share our suspicions with you. We have a feeling that Duke Stefan, the Regent, isn’t on the level. He’s the ruler until Prince Djaro is crowned, and maybe he doesn’t want Djaro crowned. Duke Stefan, the Prime Minister, and the entire Supreme Council — which is like our Congress — work hand in glove. We feel that together they may do something to prevent Djaro from becoming prince.

“Now,” Bert Young continued, “ordinarily that would be an internal political matter and this country would keep its hands off. But the rumours say Duke Stefan has something bigger in mind. And that’s as far as our information goes. We need to know what Stefan’s up to. Just maybe, if you’re living right there in the palace, you can find out for us. None of the rest of us can get close enough to the Varanians to learn the truth. Maybe Djaro knows something and is too proud to ask for help, but will tell you. Or maybe the others, thinking you’re just ordinary kids, will get careless and let something slip.

“Will you take the assignment?”

Bob and Pete waited for Jupiter, as head of the firm, to speak. Jupe thought for a moment, then he nodded.

“If what you want us to do is try to help Prince Djaro, we’ll do it,” he said. “That is, if our families will let us. But we told Djaro we’d be his friends and we won’t do anything to undermine him.”

“That’s what I wanted to hear!” Bert Young exclaimed. “One piece of advice. Don’t tell Djaro you know there’s something wrong. Get him to tell you, if possible. And don’t let anyone guess why you’re there. Almost all the Varanians are loyal to Djaro — they idolized his father, who was killed in a hunting accident eight years ago. And they don’t like Duke Stefan. But if they thought you were spying, even in a good cause, they’d raise a terrific uproar. So keep your eyes and ears open and your mouths shut.