The rain slowed to a drizzle Sunday morning. Diego borrowed a bike and a raincoat from the family of Emiliano Paz and rode into town. He met Jupiter in front of the Historical Society around noon.

“Bob’s covering the library,” Jupiter explained, “and Pete’s dad got him special permission to look at the maps in the County Land Office.”

“We’ll find Condor Castle,” Diego exclaimed. “I know it!”

They hurried into the Historical Society. People were already reading and studying at the tables of the hushed, book-lined rooms, and the assistant historian was busy. But as he directed the boys to the map room, he remarked:

“Someone else was in to look at the Alvaro papers. A tall, thin boy. He seemed to be concerned with what papers you had copied, Jupiter. Of course, I didn’t tell him.”

“Skinny!” Jupiter exclaimed when he and Diego were out of earshot. “He’s really worried about what we’re doing.”

“Because he knows all the valuable things you’ve found on other cases,” Diego said, “and he’s afraid you’ll find a treasure for us.”

“I hope we do,” Jupiter said, “but we don’t have much time.”

In the map room, the boys were alone. They found almost fifty maps from around 1846, some of the whole county, and some of just the Rocky Beach area. They didn’t find Condor Castle.

“Here’s a map of just the Alvaro ranch,” Jupiter said.

“Look how big it was then,” Diego said sadly.

“But still no Condor Castle!”

“And that’s all the maps from Don Sebastián’s time.”

“All right,” Jupiter said, refusing to give up, “we’ll look at every map of Rocky Beach no matter how new!”

“Or old!” Diego said.

There weren’t very many modern maps, and only a few from before the 1840s. Condor Castle appeared on none of them. There was nothing for Diego and Jupiter to do but give up and go back to Headquarters in the salvage yard.

“Maybe Bob or Pete will find something,” Jupiter said hopefully.

He led Diego into Headquarters by the main entrance — a large pipe that went under a huge mound of junk and ended at a trap-door in the floor of the hidden mobile home trailer.

“We call this Tunnel Two,” the stocky leader of the Investigators explained as he and Diego crawled through the pipe. “We’ve got other entrances, too, but we use this one the most. The others are for emergencies.”

“Gee!” Diego exclaimed as he emerged through the trap-door into the hidden trailer. He stared around at the desk, telephone, typewriter, files, electronic equipment, dark-room, bird-cages, plaster statues, and all the other tools and souvenirs the boys had collected in their work.

“This is great!”

“I believe we are very adequately equipped,” Jupiter said a little pompously. “We built or gathered all of it ourselves.”

“No wonder you solve tough mysteries so easily!”

“Not always so easily,” Jupiter said glumly. “Finding any clues to the Cone’s Sword seems extremely difficult.”

“Bob or Pete will find something,” Diego assured him.

As they waited impatiently, Diego wandered around the secret headquarters examining everything. He couldn’t see outside because the junk hiding the trailer was piled against its tiny windows. Jupiter sat frowning, his round face not unlike the gloomy bust of Alfred Hitchcock on the filing cabinet behind him. Then the trap-door opened, and Bob came in.

“Nothing!” the Records and Research man said, and dropped into a chair looking as gloomy as Jupiter. “I looked at every book about the county that the library has.”

When Pete finally emerged through the trap-door, the others only had to look at his face.

“If Condor Castle means anything, fellows,” the tall Second Investigator said, “I guess only Don Sebastián and José knew what.”

“We’re at a dead end, First,” Bob concluded.

Diego was near tears. “Don’t give up, fellows! We — ”

Pete sat up alertly. “Shh! Listen!”

For a long moment there was only silence inside the hidden trailer. Then everyone heard it — a faint rattle of metal outside in the salvage yard. It came again, from a slightly different spot, and then there was a sound of tapping.

“Shhhh,” Jupiter whispered, his finger on his lips.

The rattle came again — from still another spot.

“Someone is out there moving and testing the junk,” Bob said softly. “Someone who thinks we’re in here!”

“Did anyone follow either of you?” Jupiter asked quietly.

“Not me,” Bob whispered.

“I… I’m not sure,” Pete said. “I was in a hurry, I didn’t check.”

“No one moves or speaks,” Jupiter ordered.

The poking and tapping among the piles of junk that covered the trailer went on for some minutes. Then there was silence.

“Take a look, Bob,” Jupiter whispered.

The Records and Research man stepped softly to the See-All, a homemade periscope that went up through the roof. From outside, it looked like a simple piece of old pipe sticking up at the top of a junk mound. Bob looked through the eyepiece.

“He’s going away across the yard,” Bob reported. “It’s that ranch manager, Cody! He’s still looking around. Now he’s leaving the salvage yard. He’s gone, fellows!”

Bob turned from the See-All. “He must have followed one of us to see what we’re doing. Jupe, could he have been the eavesdropper at Emiliano Paz’s place yesterday?”

“I suspect as much,” Jupiter said thoughtfully. “Skinny and that Cody seem very interested in our actions. I wonder if they have any more reason than to help Mr. Norris get the Alvaro ranch?”

“Maybe they know something about the sword and want to find it for themselves!” Diego exclaimed.

“That is possible, Diego.”

“If they know anything, it’s more than we do,” Pete said.

Jupiter nodded sadly. “I was certain we would find an old map that would tell us what and where Condor Castle was.”

“Maybe we need an old Indian map, and an old Indian to read it for us.” Pete laughed.

“Very funny, Second,” Bob groaned. “Jokes won’t help us — ”

“Pete!” Jupiter cried. “I think you’ve got it!”

“Gosh, First, it wasn’t that bad a joke. You don’t have to — ”

“No,” Jupiter said, “I mean it! That could be the answer! Of course, I’ve been stupid!”

“What answer, First?” Pete said, confused.

“A really old map! If Don Sebastián had used a name everyone could find on a map in 1846, the Americans would have spotted it! He knew they would study the letter — so he used a name from a map so old and rare even in 1846 only he and José would recognize it! I never thought to ask the historian for really old maps — and they’d be too valuable just to leave out in the map room. Come on! Back to the Historical Society!”

They scrambled out through Tunnel Two, checking carefully at the end of the pipe to be sure that Cody, or anyone else, wasn’t watching. Jupiter led the race to their bikes.

As the boys rode out of the salvage yard, a voice boomed across the street:

“JUPITER!”

Aunt Mathilda was standing on the stoop of the Jones house looking angry.

“Where have you been, you scamp! Have you forgotten your great-uncle Matthew’s birthday party? We have to leave in fifteen minutes! Get over here and put on your good suit! You’ll have to see your friends another time.”

“Oh, no!” groaned Jupe. “I forgot! It’s my great-uncle’s eightieth birthday,” he explained to his friends. “There’s a family party for him clear on the other side of Los Angeles. I can’t get out of going, and I’m sure we won’t be back until very late. You’ll have to carry on without me.”

“Jupiter!” Aunt Mathilda’s voice held an ominous warning note.

Jupe sadly waved goodbye to the other boys and went across the street.

“Now what?” asked Pete.

“To the Historical Society, of course,” answered Bob, taking charge. And in a minute, the boys had forgotten all about Jupiter as their excitement over Condor Castle rose again.