Pete looked towards the woods beyond the meadow. "Okay," he said. "Let's go see where."

The Three Investigators went first to the place where Jupiter had taken a cast of the footprint. Then they walked slowly on. They found no more prints until they were in under the trees. There was one low-lying spot where the earth was bare, and, sure enough, the shoeless wanderer had come that way. Pete pointed to the print. The Three Investigators skirted it and pushed on without a sound, moving stealthily as if someone might be lurking behind a tree, waiting to strike down a pursuer.

Finally the trees thinned, and beyond them was a clearing. The boys stood at the edge of the wood and looked out at gra.s.s and at brambles that surrounded the crumbling remains of an old building. It had walls of brick that were broken in several places and a red tile roof that had fallen in here and there, so that some of the supporting beams could be seen.

"Once upon a time," Bob observed, "I think that must have been a church."

No one answered him, and the three boys crossed the clearing.

Two great wooden doors had once closed the entrance of the church, but one of them had fallen off its hinges. It lay inside on the tile floor. The boys stepped over it as they entered the building.

"Do you suppose the barefoot cave man came in here last night?" said Pete. He looked around nervously.

"No way of telling," said Jupe. "He wouldn't leave any traces on this floor."

Bob made a hesitant movement towards the front of the church. Two steps there led up to a place that was higher than the area where the boys stood.

"If there was an altar," said Bob, "it would have been up there. And look. There's a doorway that must lead into another room. Maybe it was a vestry where the priest or the minister could put on his robes."

The Three Investigators waited in the silence, each one somehow unwilling to cross the church and go up the two steps and open the door to the hidden room.

Suddenly they heard a sound that made their hearts beat faster.

Someone was moving behind the closed door! There was a creaking and a rustling, and something fell clattering to the tiles.

Then there was stillness.

Pete stepped backward, as if he might run. Bob made a move towards the closed door, and Pete caught his arm.

"Don't!" whispered Pete. "Suppose it's ... "

He didn't explain. He didn't have to. The other two understood. Suppose the cave man had walked again. Suppose he had escaped from the captor who held him for ransom, and the long-dead bones had somehow a.s.sumed flesh once more, and the ancient creature was there, crouched in the hidden room, armed! Armed? With what?

"Impossible!" said Jupiter bravely. He ran forward and went up the two steps. As he did so, there was another noise - a noise as if something had touched the door, rattling it slightly.

Jupe put his hand on the doork.n.o.b, and then he froze. A p.r.i.c.kle of horror stirred his scalp.

The k.n.o.b was turning under his hand. It was turning by itself! Then the old hinges groaned in protest, and the door began to open!

"Good night!" exclaimed Dr. Hoffer, his hand still on the k.n.o.b of the vestry door.

"You startled me. I didn't know anyone was here."

Jupiter was still trembling, but he managed to smile. "We were exploring," he said.

Hoffer walked through the vestry door into the church. The boys could see that there was a small room behind him, with a door leading to the outside.

"You boys want to be careful," said Hoffer. "This is private property. It belongs to the Lewison family. They own a big house on the far side of the hill. I have permission to come here, but I don't think they like strangers."

He sat down on the steps that separated the altar area from the rest of the church.

"It's amazing how things never really change," he said. "There is an empty building in the neighbourhood, and I find you three exploring it. I would have done the same thing when I was a youngster. When I was your age, there was a vacant house up our neighbourhood in Milwaukee. We found unlocked windows and we got in and established a clubhouse in the cellar. It was very pleasant there - not infested with people like parents and teachers."

Dr. Hoffer stopped and sneezed. He took out a handkerchief and dabbed at his eyes.

"It's that hay fever again," he said. "I'm always having allergic reactions to things.

It's what prompted my interest in immunity."

He stood up. "This is as far as I'll go today," he said. "Something in the air isn't agreeing with me. Are you boys coming back to the village? If I were you, I don't think I'd explore further. Edward Lewison has been known to take a shotgun to trespa.s.sers."

"Like somebody else we know," said Jupe. "Newt McAfee."

"Then let's go back to the village," said Pete.

The boys followed Dr. Hoffer out through the vestry.

"You're interested in allergies?" said Jupe as they plunged into the woods. "But you became an immunologist. I thought people who took care of allergies were allergists."

"They are," said Hoffer. "However, one thing leads to another. An immunity is a sort of allergic reaction."

"It is?" said Bob.

Hoffer nodded. "Our bodies have various ways of defending themselves. They can produce things called antibodies. The antibodies destroy invading viruses and bacteria, or they cancel the poisons that come from the tiny invaders. If you get German measles, for example, your body will produce antibodies to fight the disease.

Once that happens, you won't get the disease again because the antibodies remain in your system. So we say that you're immune to German measles.

"Now suppose your body produces antibodies in reaction to things that don't bother most people. Say you're allergic to a certain pollen. Your body will produce antibodies that react with the pollen, and it will release a chemical compound called histamine. This makes your nose swell and your eyes water.

"So our immune system saves our lives when it fights disease, but it can make our lives miserable when it gets out of control. I believe that many more human ills are due to breakdowns of the immune system than is commonly thought.

"Suppose a person's body produces chemicals that make his joints swell up, the way the mucus membranes of the nose swell up when a patient has hay fever.

Arthritis, eh? Why wouldn't that be an allergic reaction? And cancer? There's a virus theory of cancer. Why not an allergy theory? Cancer consists of cells growing out of control, possibly in response to something harmful. And crime!"

"Crime?" echoed Pete.

"Crime can be a reaction to a threat," said Dr. Hoffer. "Imagine a person growing up in a dangerous place. To protect himself, the person develops a reaction to the approach of any stranger - a violent reaction. Without even thinking, he will attack before he can be attacked. The defences have run wild."

Dr. Hoffer looked grim. "The defence system is our greatest a.s.set, and our greatest threat too. I have rats in the laboratory that live sealed behind gla.s.s part.i.tions, protected from infection. I have been able to short-circuit their immune systems, and they will live much longer than unprotected rats. Of course, they are especially open to disease because they have no defences. But if I could learn to modify their reactions, to regulate their immunities, they could exist outside the gla.s.s cages and still avoid many of the ills that kill their fellows.

"Now imagine what controlled immunities could mean to humans. Think of a world without all those terrible diseases!"

Hoffer nodded. "Worth any effort!" he said. "What Birkensteen was doing with intelligence was completely visionary, and probably dangerous as well. And Brandon is a child playing with dusty bones. What I am doing is practical, and it could have tremendous impact almost immediately."

They had reached the field behind the McAfee house. Hoffer paused to shake hands with the boys. Then he went on to the road and up the hill towards the foundation.

There was a stunned silence as he left. Then Pete said, "Okay. I'm convinced. I nominate Dr. Hoffer for the million dollars from the Spicer Grant."

Jupe just nodded, and the boys went on down the street to the cafe.

The crowd in the town was thinning out now, and there was no long wait for a table. The boys ate an early dinner, talking quietly among themselves about the events of the day.

"A weird case," was Pete's conclusion. "Really squirrelly. The whole town falls over in a dead sleep, and a cave man takes a stroll."

"And we have the cave man's footprint, if that's who it was," said Jupe. "What can we learn from it? What would you think of showing it to Dr. Brandon? He's used to deducing things from clues like a bit of bone or a footprint preserved in mud. If there could be a connection between the footprint on the meadow and the cave man, he would recognize it instantly."

"Jupe, it couldn't be the cave man," said Bob.

"Perhaps not, but there was a barefooted person on the meadow, and John the Gypsy swears he saw a cave man, and Dr. Brandon certainly would be interested to know that, wouldn't he?"

"Okay," said Bob. "I guess it's worth a try."

The boys finished their meal and hurried up the street to the barn, where they took the cast of the footprint from Jupe's sleeping bag. Then they went on to the Spicer Foundation. They found James Brandon in his workroom.

Brandon was sitting at a desk strewn with papers and books. He glared at the Three Investigators when they came in. The boys almost feared that he was about to fly into one of his shouting rages. However, once he closed the book he was reading, they could see that he was not really angry, just deeply involved with what he was doing.

"Well?" he said. "What is it?"

"We want some advice," said Jupiter, "and perhaps some information. Dr.

Brandon, we have been staying in the loft in Newt McAfee's barn, and we can see the museum from the window there. Last night, very late, there was a disturbance there."

Jupe went on to tell of John the Gypsy's strange experience and of finding the footprint on the meadow. Then he showed the cast of the footprint to Brandon.

"Of course, it is impossible to believe that the cave man walked in the meadow,"

said Jupiter. "But someone did, and you are accustomed to deducing facts about a person with far less evidence than this."

Brandon smiled. "When you talk that way, I get the feeling that I have been marooned in a nineteenth-century detective story." He put the cast on his desk.

"Well, if you were hoping for a prehistoric creature, this isn't it," he said. "The person who made this footprint is used to wearing shoes. When a person goes barefoot all the time, the feet spread and the toes splay out. But the person who made these prints had narrow feet. Also, he has a hammer toe, which is unlikely for someone who doesn't wear shoes."

"John the Gypsy said it was a cave man, though," said Bob. "He said it had long s.h.a.ggy hair and was wearing an animal skin."

James Brandon chuckled. "Do you really suppose that prehumans wore clothes? I don't know what John the Gypsy thinks he saw, but the person who made this print is not the cave man. Not only are the feet too narrow - even a.s.suming that a dead hominid could wander around - but the feet are too big."

"Too big?" Pete looked startled. "But they're small! Only nine inches."

"Primitive beings were very small," said Brandon. "I took measurements of the fossil in the cave, and from the size of the bones, I would say that our cave man was about ninety-five centimetres tall when he was up and walking around. That isn't much more than three feet. The individual who made this footprint had to be at least five three or four."

Brandon went to a cabinet that stood against the wall. "When I was in Africa," he said, "I was fortunate enough to find an almost complete fossil skeleton that dates back almost two million years. It is slightly smaller than the Citrus Grove hominid, but it will give you an idea."

Brandon unlocked the double doors of the cabinet and swung them wide.

Then he stood as if frozen, gaping at the empty shelves in front of him.

"It's gone!" he said in a whisper.

Then, taking a deep breath, he shouted, "Gone! It's gone! Someone's stolen my hominid!"

Chapter 13.

The Dead Man's Note JUPITER WON A SMALL victory over Newt McAfee that evening. He announced that since so many of the tourists who had come to Citrus Grove for the opening of the cave were gone, he and his friends would move from the loft to the campground.

McAfee hastily lowered his fee from ten dollars to three and the boys paid the money and retired to the loft chuckling.

For a while they lay in the darkness, pondering the events of the day. At last Pete said, "It's wild. Open season on old bones."

"I wonder when Dr. Brandon's fossils were taken," said Bob. "He's been so busy with other things that he hasn't looked at them for two or three months."

"That would put it back in the spring," said Jupe, "about the time Dr. Birkensteen died."

Pete groaned. "Not that again. Birkensteen had nothing to do with fossils. There's no connection, except that he lived here."

"There's Eleanor Hess," said Jupe. "Is she lying about that trip to Rocky Beach?

She knew they were looking for an address on Harbourview Lane. Wouldn't it be logical for her to know what the exact address was and who lived there?"

"True," said Bob. "And she won't look right at you when she talks about it."

"And why are the pages missing from Birkensteen's calendar?" Jupe persisted.

"What notations did Birkensteen make on those pages? Did he tear out the pages himself, or did someone else?"

"Hey!" Pete sat up in his sleeping bag. "Suppose Birkensteen was in touch with someone in Rocky Beach, and he just happened to mention the cave man. Couldn't he have planted the idea of the theft there? We've been acting like someone in Citrus Grove had to be the thief, but maybe that isn't true. The town was crawling with visitors today!"

"That might be possible," said Jupe, "except Brandon didn't discover the cave man until after Birkensteen died."

"Oh," said Pete.

"There still could be some connection, though," said Jupe. "Maybe just less direct.

If we only had those missing calendar pages. And Birkensteen's notes. The notes on his work in the last days might have a clue."

"Or there might be a clue in Rocky Beach," said Bob. "You said Birkensteen was looking for Harbourview Lane. I know that street. It's a short dead-end street off Sunset. Suppose I go to Harbourview and ring doorbells and say that Dr.

Birkensteen's briefcase is missing, and ask if he left it when he came in May. Of course, he never got where he was going, but I sure ought to get a reaction if someone from Harbourview Lane knew him. I'll take the early bus in the morning. I can be in Rocky Beach in a couple of hours."

"Very well," said Jupe. "I'll go back to the foundation to see if I can find Dr.

Birkensteen's papers. Dr. Brandon might help me. He seemed friendly enough this evening."