“Take it up with him tomorrow! I have to go now!” And the phone at the other end was hung up with a bang.

Jupiter hung up also and looked blankly at Pete and Bob.

“Something tells me,” Pete said, “that Lieutenant Carter doesn’t like us.”

“He sounded as if he didn’t like anybody,” Bob put in. “Especially kids.”

“His attitude is quite common among adults,” Jupiter said with a sigh. “They think that just because we’re young we don’t have any good ideas. Actually, we often have a fresh viewpoint on a problem. But I guess we can’t take the trunk down to Chief Reynolds before tomorrow — maybe not even then, because tomorrow’s Sunday. We may have to wait until Monday. So I suggest we search the trunk again and try to find that clue Socrates mentioned.”

“I’m tired of that trunk,” Pete said firmly. “I’m tired of Socrates. I don’t want him talking to me.”

“I don’t think he’ll talk to us any more,” Jupiter replied. “Somehow he doesn’t seem to talk face to face. He talked to me in the dark in my room, and from inside the trunk, but never directly.”

“He said ‘boo’ to your aunt,” Bob pointed out.

“Yes. I can’t explain that,” Jupiter admitted. “But suppose we open the trunk and have a look. Perhaps someone took something out before returning it.”

They crawled out through Tunnel Two and opened the trunk. The interior looked just as it had before. Socrates, well wrapped in old velvet, was snugly in a corner. The letter was still in place inside the tear in the lining.

Jupiter took Socrates out, unwrapped him and set him on his ivory base on the printing press. Then he picked up the letter.

“Let’s have another look at this,” he suggested.

All three read the letter again. It seemed as innocent as before.

State Prison Hospital July 17 Dear Gulliver:

Just a few words from your old pal and cellmate, Spike Neely. I’m in the hospital, and it looks like I haven’t got much longer.

I may last five days or three weeks, or even two months, the doctors aren’t sure. But in any case, it’s time to say good-bye.

If you’re ever in Chicago, look up my cousin Danny Street. Tell him hello for me. Wish I could say more, but this is all I can manage.

Your friend,

Spike

“If there’s a hidden clue there, I can’t find it,” Jupiter muttered. “I wonder if — Wait! I’ve found something. Look!”

He held out the letter and the envelope to Bob. “Do you see what we missed?”

“What we missed?” Bob looked puzzled. “No, I don’t see anything special, Jupe.”

“The stamps on the envelope!” Jupe said. “We didn’t look under the stamps for a message!”

Bob looked at the two stamps — a two-cent stamp and a four-cent stamp. He took the envelope and ran his finger over them. His expression changed to one of great excitement.

“Jupe!” he exclaimed. “You’re right! There’s something under one of these stamps. The four-cent stamp feels just a little bit thicker than the two.”

Pete also ran his finger over the stamps and nodded.

The four-cent stamp was just a trifle thicker — not enough for the eye to notice unless you looked very closely.

“Let’s get inside Headquarters and steam these stamps off and see what’s underneath!” Bob exclaimed.

They scrambled back through Tunnel Two and within three minutes had a little kettle boiling in the laboratory. Jupiter held the corner of the envelope in the steam until the stamps loosened. Then he gave a shout of excitement.

“Look!” he cried. “There’s another stamp underneath the four. A green one-cent.”

“That’s queer.” Bob frowned. “What does it mean, Jupe?”

“I can tell you what it means,” Pete said. “There’s nothing mysterious about it. Don’t you remember that back about the time this letter was mailed, the postage rates went up by a cent? Spike Neely probably put a one-cent stamp on then realized that wouldn’t be enough so he pasted on a two, then put the four-cent stamp on top of the one.”

“Gosh, that could be right,” Bob said. “I think Pete has hit on it, Jupe.”

“I’m not so sure.” Jupe scowled at the green stamp on the envelope. Then, carefully, he peeled it off. “There may be writing underneath it,” he said.

“No,” Bob announced when the stamp was off. “No writing. None on the back of any of the stamps either. What do you say now, Jupe?”

“It’s too peculiar to be an accident,” Jupe said, still scowling. “It has to mean something.”

“Then what?” Pete demanded.

“I’m thinking,” Jupiter said. “Spike knew this letter would be censored. So I deduce he used the stamps to send his message. He put one stamp under another stamp, so neatly it wouldn’t be noticed. He expected Gulliver to examine the whole letter very carefully and find it. I deduce that the one-cent stamp being green, the colour of U.S. paper money, stands for the missing fifty thousand dollars. What Spike meant —”

He broke off, thinking hard. Bob’s shout broke the silence.

“I’ve got it!” he yelled. “A stamp is a piece of paper, see? Money is paper, too. Spike put a piece of paper underneath another piece of paper. Spike was telling Gulliver that the money was hidden somewhere under some paper.

“Mrs. Miller told us that while Spike was hiding out in her old house, he papered the whole downstairs! That was when he hid the fifty thousand dollars. He put the bills side by side and pasted them underneath the new wallpaper!”

“Wow!” Pete said admiringly. “Bob, you’ve got it. That has to be the answer, doesn’t it, Jupe?”

Jupiter nodded. “Yes,” he said. “Remarkable deduction, Bob. I’m just remembering a story I once read. It’s a mystery story by a man named Robert Barr. In it a character named Lord Chizelrigg hides a lot of gold beating it into gold-leaf and pasting it under some wallpaper. The principle is the same. Only Spike Neely used paper money, which is much easier to handle.”

“But wait a minute!” Bob put in. “Mrs. Miller said Spike Neely went out and finished a job for Mr. Miller. Maybe he hid the money there.”

“I don’t think so.” Jupiter shook his head. “The best place would be — Oh! Oh! Oh!”

“Oh! Oh! Oh! what?” Pete asked. “What’re you oh-ing about, Jupe?”

“Spike tells us! That is, he told Gulliver. Right in the letter. Look at it!” Jupiter handed the letter over to Bob and Pete.

“See what he starts off by saying. ‘I may last five days, or three weeks, or even two months.’ Take those numbers and put them together. They make 532. What does that remind you of?”

“That was the number of Mrs. Miller’s house!”Bob shouted. “532 Danville Street.”

“Right,” Jupiter said. “And look here. He tells Gulliver, ‘If you’re ever in Chicago, look up my cousin Danny Street.’ ”

“Danny could be a nickname for Danville!” Pete exclaimed.

“Right!” Jupe agreed. “That mention of a cousin, and Chicago is just put in to distract attention from the words Danny Street. As near as he dared say it, Spike Neely was telling Gulliver that the money was hidden at 532 Danville Street.”

“Under the wallpaper!” Bob chimed in. “He didn’t dare say too much, but that was very tricky, putting one stamp under another!”

“We’ve solved the riddle,” Pete said, jubilant. Then he looked thoughtful. “Now how do we find the money?”

“If it’s underneath somebody’s wallpaper, we can’t just barge in and say, ‘Excuse us, we have to rip your wallpaper off,’ ” Bob remarked.

“No,” Jupiter agreed. “That’s a job for the police. We’ll have to tell Chief Reynolds. It’s no use trying to tell Lieutenant Carter — he made it plain he doesn’t want us bothering him. Tomorrow, though, or Monday, when the Chief is back —”

The ringing of the telephone interrupted him. Startled, Jupiter picked it up.

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