Dr. Jordan was in the middle of talking to the students about mummification when Cody slipped into the back of the workroom. Matt the Brat spotted her, and made a face. She ignored him. Cody saw Ms. Cassatt fiddling with her pendant again, while she watched from the sidelines, her eyes darting around the room. Cody noticed how fidgety Ms. Cassatt seemed, while Dr. Jordan appeared completely at ease.

Strange, Cody thought, then she returned her attention to the presentation.

Dr. Jordan stood behind the counter where, earlier, he’d been cleaning the Eye of Horus amulet. In front of him lay a small wooden container the size of a shoe box, covered with faded hieroglyphs that looked as if they had lost their vibrant colors over time.

Cody shivered. She wasn’t sure she wanted to see what was in the box after all.

Too late.

Dr. Jordan lifted the top and tilted the box toward the students. Cody glanced inside and saw the small mummified body of a cat. It looked black, bony, and stiff—and totally creeped her out.

“This is Ta-Miewet,” Dr. Jordan announced proudly, as if he were introducing an old friend. “He’s a mummified cat who was buried with his owner about six thousand years ago. Back then, Egyptians thought cats were magical and could protect them. They even adorned their cats with expensive, ornate jewelry. Believe it or not, all domesticated cats are descendants of Egyptian cats—even yours.”

Cody thought of her cat, Punkin. Was he magical? Did he protect her? No, she decided. Just another superstition.

M.E. whispered in her ear, “You need to get some earrings for Punkin!”

Cody smiled at how ridiculous that sounded. But it was definitely something that M.E. would do for her pets. She was a big fan of jewels, sequins, and glitter.

“Would you like to know how mummies are made?” Dr. Jordan asked.

The group responded eagerly. Cody’s stomach tightened.

“All right, but this might be a bit gruesome.” He grinned. The light glinted off his nose ring.

“First, the body is washed and cast with magical spells for protection. All the organs are removed, except for the heart. Wine is poured over the body to disinfect it. The organs are covered with salt and baking soda, and set out to dry. Then they’re placed in vessels called canopic jars. The body is perfumed and wrapped up tightly, and good-luck amulets are added. Finally, the body is placed in a coffin—called a sarcophagus—that is often painted to look like the deceased and adorned with hieroglyphs. Once the process is finished, the body can stay intact for centuries.”

“Why did they do all that?” asked Jodie from Mr. Pike’s class. “Why not just bury them like we do now?”

“The Egyptians believed this process would ensure them a happy afterlife,” Dr. Jordan said.

“Weird,” Jodie mumbled.

“Well, certainly different from our customs today,” Dr. Jordan said. “The Egyptians never cremated bodies. They preserved them in preparation for the afterlife. And not everyone was allowed in. You had to serve some purpose, like the pharaoh. They believed he became a type of god after he died.”

Dr. Jordan pointed to the mouth of the cat. “After the mummy was prepared, a priest touched its mouth with a blade, to ensure the mummy could breathe and speak in the afterlife. This part of the ceremony was called reanimation.”

“I saw a movie about that,” Matt said. “This mummy came back to life and started going after all the people.”

Dr. Jordan didn’t seem to hear Matt. He continued explaining the burial ritual. “After they recited prayers and burned incense, the mummy was placed inside the pyramid, along with lots of food, clothes, jewelry, and even furniture, to make the afterlife more comfortable. Then the pyramid was sealed, never to be entered again. That is, until tomb raiders came along.” Several students murmured excitedly at the mention of tomb raiders.

“Any questions?” Dr. Jordan asked the group.

When no one raised a hand, Cody started thinking about the open display case and the still-wet coloring on the Eye of Horus. The Code Busters didn’t have any proof that the Eye was a fake—only circumstantial evidence. Her dad was a lawyer and he’d talked about circumstantial evidence a lot. Basically, it meant that there were clues leading to a fact, but nothing concrete that could absolutely prove that fact. It was like if your little sister had a chocolate milk mustache but swore she didn’t take the last carton. It was possible that she got her mustache drinking the milk at a neighbor’s house. That’s circumstantial proof. But if her fingerprints were found on the fridge and the empty carton, that would be what her dad called “corroborating evidence.” That plus the mustache might prove the crime.

Fingerprints.

That gave Cody an idea.

If she could prove that Dr. Jordan’s fingerprints were on the Eye and the case, wouldn’t that mean he could have switched the artifacts?

No, she decided glumly. He obviously touched the Eye and the case when he went to get the amulet for cleaning. In fact, his fingerprints would be all over the place.

And besides, she still didn’t know for sure if the Eye in the case was real or not. She thought it was a fake because of the brown stain that came off on their fingers. Now that the case was relocked, the Code Busters couldn’t even prove it had ever been open.

That brown coloring had to be proof of something. But Dr. Jordan could argue that the girls must have touched something on the work counter in his lab.

Thoughts bounced around in Cody’s head like pebbles during a sandstorm. She was getting nowhere. All this talk of mummies, and forgeries, was feeding her already active imagination.

“Students!” Ms. Stad called out after Dr. Jordan was finished answering questions about mummies. “Let’s give Dr. Jordan a round of applause for his wonderful presentation! That was fascinating.”

The group clapped enthusiastically.

“I still want to see a real mummy,” Matt grumbled. Ms. Stad hushed him.

“Now, turn in your papers, if you haven’t already. Then you’re free to go to the gift shop. Those of you who won the prize, come see me. I’ll have something special for the group that solved the most puzzles when we gather in half an hour.”

Ms. Stad gave each of the Code Busters a rolled-up sheet of paper. Cody unrolled hers and smiled at the painting inside. “These are hand-painted pictures on real papyrus,” Ms. Stad explained. “Each one is different.”

Cody held hers up for the others to see. It was a painting of the Eye of Horus. M.E. unrolled hers to find a painting of a sarcophagus. Luke showed his—a picture of a pyramid. And Quinn got a picture of the Rosetta Stone.

“Awesome,” Quinn said. The others nodded, pleased with their prizes. They rolled them back up and stuck them carefully in their backpacks. As Ms. Stad stood there talking to some other students, Cody opened another compartment in her backpack and pulled out her Code Busters notebook. She wrote a message in Morse code, added her code name at the end, then tore it out and passed it to M.E. It read:

Code Buster’s Key and Solution found on this page, this page.

M.E. read the note, then passed it on to Quinn, who passed it to Luke. While Ms. Stad and the other students browsed the gift shop for Egyptian trinkets to buy, the Code Busters slipped away and headed for the workroom in the back of the museum.

Cody glanced around to make sure no one saw them. She tried the knob. It opened. She waved the others to follow her inside.

The room appeared empty. No sign of Dr. Jordan.

Cody whispered, “If the Eye of Horus in that case is fake, then maybe the real Eye is in here somewhere. Dr. Jordan could have hidden it for safe-keeping, planning to come back for it later when the museum closes. Maybe he’s going to sneak it out and take it with him when he leaves for the day, like that thief Ms. Cassatt told us about. We have to find the real Eye if we’re going to prove that the one in the case is a fake.”

“Cody, we could search this place all day and not find anything,” M.E. whined. “There are too many places to hide something that small. It could be anywhere.”

“She’s right,” Quinn said. “We have to think about this logically. Where would we hide something like that if we stole it?”

Cody looked around at all the tables, cupboards, shelves, and desks. There was no way they’d find the Eye if it was hidden in this room. There were just too many places to search, and no time to do it. This was hopeless. Talk about a riddle that was impossible to solve: Where would you hide an Eye that can’t see?

She thought about the riddle that was written on the bottom of the artifact: “an eye for an i.” Was that a clue? Dr. Jordan said that many forgers were proud of their fakes and left a “calling card”—a symbol or message meant to brag about their expertise, and even possibly identify them. Ms. Cassatt said that like Leonardo da Vinci, one forger used to leave his initials hidden in the artwork. Another one always wrote the names of his children in the picture, and then disguised them. And another used to sign his name, then paint over it so no one could see it. Dr. Jordan said it was detected by using infrared and ultraviolet fluorescent light.

Cody heard Ms. Stad calling all the students from the lobby.

“Uh-oh. Time to go back,” she said, disappointed they hadn’t solved their mystery. She was just about to follow the others out when she had an idea and ran back to the counter where Dr. Jordan had been working. Behind it was a wastebasket, filled with wrinkled papers, soiled cloths—and latex gloves.

Cody retrieved the pair of gloves from the top of the pile. The fingertips were smudged brown. She stuffed the gloves into her hoodie pocket and returned to the lobby with the others to rejoin their classes.

“Listen up, everyone,” Ms. Stad called out. “Mr. Pike and I have reviewed all your answers to the codes, questions, and riddles from earlier. And we have a grand prize winner! The group that had the most correct answers and now gets a sneak peek at the next planned exhibit with Ms. Cassatt is … the Code Busters!”

“Yes!” Quinn and Luke’s fists shot in the air. Cody and M.E. high-fived each other.

Winning this reward lifted Cody’s spirits. At least she and her friends would get to see something the other students wouldn’t until their next visit to the museum. She hoped Ms. Cassatt would show them some cool artifacts, and maybe even a mummy.

“Quiet down, please,” Ms. Stad continued after her announcement. “Not only did they find the most Eyes of Horus throughout the museum—thirteen, one more than the parent volunteers found, in fact—but they also solved all of the puzzles! Great job!”

Wait a minute, Cody thought. Something’s wrong. An alarm sounded in her head.

She did the math again to make sure. Ms. Stad said there were originally twelve Eyes. But they had found thirteen. Maybe the parent volunteers didn’t count wrong. Maybe another Eye of Horus had been added to the collection. A fake? If so, maybe the real one wasn’t hidden in the workroom. Maybe it was hidden right in front of their eyes!

“All right, students,” Ms. Stad announced. “Now that Cody, M.E., Quinn, and Luke are back from their preview, it’s time to reboard the bus and head back to school. Find your buddy and line up, please.”

Cody shot a panicked glance at M.E. It had been cool seeing the upcoming exhibit, but she’d hoped to get a chance to search the museum for the extra Eye. She finger-spelled a message so no one would overhear her:

M.E. frowned at her friend and finger-spelled:

Code Buster’s Key and Solution found on this page, this page.

Cody ignored her friend and signed, “Hurry!” then went to find her teacher while M.E. passed the message along to the boys.

“Ms. Stad!” Cody called, elbowing through the crowd of students who were lining up for the bus.

“What is it, Cody?” Ms. Stad asked, as she counted heads. “You and M.E. need to get in line. We’re leaving in five minutes.”

“I … I,” Cody stammered. She couldn’t tell Ms. Stad her suspicions without proof. Her teacher would think she was crazy. But she had to check out the rooms again to make sure she was right. “I … left my cell phone in one of the rooms. I need to find it! M.E. and Luke and Quinn said they’d help me. It’ll only take us a few seconds. We’ll be right back!”

Before Ms. Stad could respond, Cody raced to meet her friends at the entrance of the Daily Life room. She hoped her little white lie would buy her enough time.

“Find all of the Eyes you can!” Cody ordered the puzzled Code Busters. She held up the cell phone snapshot of the Eye that was in the unlocked case. “Look for one that’s the same as this.”

“Why are we doing this?” M.E. asked, while the boys began searching.

“I think there’s an extra Eye somewhere that doesn’t belong. Remember when we counted the Eyes and found thirteen, when Stad said the parent volunteers only found twelve? Well, the thirteenth one has got to be the real Eye of Horus, added after the parents counted them. If we find it, then maybe we can prove the one in the case is a fake. I think Dr. Jordan hid it with the other artifacts, figuring it would blend in and no one would notice it. I’m sure it’s been right in front of our eyes the whole time.”

The girls joined the boys in their search, but none of them found a match in the Daily Life room.

“Follow me,” Cody said, racing to the Burial Practices room. After a quick but thorough search that turned up nothing, they moved on to the Gods and Religion room, and finally to the Kings and Pharaohs room.

And then, inside a case filled with jewelry worn by Egyptian royalty, Cody spotted a statue of a cat painted with hieroglyphs and covered in jewelry. “Look!” she said, alerting the others. “See that cat?”

M.E. peered into the case. “The one with all the necklaces, and earrings, and a tiara? I wish I had all that stuff. What about it?”

“Look closely.”

M.E. blinked. “Wow. I didn’t even notice it before.”

“What?” Quinn asked.

M.E. pointed. “Look what’s hanging around that cat’s neck. A bunch of necklaces, including an Eye of Horus!”

“Yes!” Cody said. “And it’s identical to the one in the case. It probably wasn’t there when the parents checked. I’ll bet none of the other kids saw it because that cat is wearing so much jewelry. It just blends in.”

Cody held her cell phone picture up to the display case to double-check.

The amulet was identical.

“That’s it!” M.E. squealed. “We found it!”

Before Cody could respond, she heard footsteps behind them. She lowered her cell phone and froze.

“Found what?” came a deep voice.

The Code Busters turned around slowly. Standing in the doorway was Dr. Jordan.

There was no smile on his face this time. His eyebrows were drawn together.

“What are you kids doing in here?” he said, ominously, his dark eyes reflecting his sudden dark mood. “I thought you’d left.”

Thinking fast, Cody suddenly lifted her arms out like an airplane, then jerked them up to form a giant Y, and finally dropped them down as if framing a full skirt. She was signaling her friends.

Code Buster’s Key and Solution found on this page, this page.

They all raced from the room.