“Students don’t have to pay, so we can use this entrance.” Hem waved Anna, José, and Henry through a gate into the Louvre’s big, open lobby and pointed up a wide set of stairs. “We’ll start in the Denon wing.”

“Start what?” Henry hoped this wasn’t going to be like one of Aunt Lucinda’s marathon museum visits.

“My personal tour of the Louvre. I want to see for myself what’s missing. Mum and the other society members talked about a Vermeer and a Monet, but the museum said there were smaller pieces stolen, too.”

They all followed Hem up the stairs, but only Anna looked excited about the tour.

“Here’s stop number one,” Hem said, gazing up at a headless marble statue with wings. “Winged Victory.”

“Wow,” Anna said.

“Does the museum know her head got stolen?” Henry asked.

“Henry!” Anna gave him a look.

Hem laughed. “The sculpture was like this when it was discovered on a Greek island. It’s been here since 1884. Except for a few years during World War Two …” He lowered his voice. “Society members moved Victory and a bunch of other pieces out of Paris to keep them safe from the bombs.” He pointed up another set of stairs to the right. “Come on, let’s go see the Mona Lisa before the room gets too busy.”

Hem took the next set of stairs two at a time, led them through a hallway of old Italian paintings he called frescoes, and stepped into a long gallery full of paintings and sculptures. There was one of a mom with an infant, and it reminded Henry of his new baby sister. When would his dad call? He was probably still really busy with the baby. But didn’t he wonder how Henry was doing in Paris, way across the ocean? Henry looked away from the painting and hurried to catch up with the others.

“Is the Mona Lisa up there?” Anna pointed to a group of people ahead.

“No,” Hem said, squinting. “It’s … oh.” His voice fell. “It was a painting called Old Man with a Young Boy.”

He led Henry, Anna, and José through the crowd to an empty spot on the wall.

“Was it a well-known painting?” José asked.

Hem shook his head. “That’s the weird thing. It’s not super-famous like the Mona Lisa or anything, but I fancied it.” He blinked fast, and Henry felt a little bad for Hem, even though he still hated his accent and that he used words like fancied.

“Let’s keep going. She’s in here.” Hem directed them into a big room with one area roped off. Behind the ropes, a thick wooden semicircle of railing — almost like a counter where you’d order ice cream — surrounded an empty glass box.

“Umm …” Henry had heard people say the Mona Lisa was smaller than you’d think, but he couldn’t see anything in that case. He turned to Hem. “Dude … where is she?”

Hem’s face filled with alarm for a second. Then he hurried over to the guard at the edge of the railing. They talked, and the guard gestured toward the empty glass case, then off to the side.

“Well?” Anna asked when Hem returned.

“Everything’s okay,” Hem said. “They’ve taken her for some restoration work.”

Henry frowned. “They move the Mona Lisa around like that? Isn’t it a security risk?”

“I know, right?” Anna agreed. “Like the Jaguar Cup …” The golden cup had been stolen in Costa Rica, on its way to an international exhibit.

“And that painting in the book Chasing Vermeer,” José added. “The girl writing the letter? Wasn’t that out on loan when it was stolen?”

Henry nodded. “Same thing happens in my Super-Heist game when the museum sends the Starry Night painting to get re-starred.”

“There’s a video game where Starry Night gets stolen?” Anna asked.

“Totally,” Henry said. “There are like a dozen paintings to steal. If you win, you go back to your sim house at the end and decide where to hang ’em all.”

“But that’s fiction, and so is the Vermeer thing, actually.” José looked at Hem. “When the Mona Lisa is being restored, do they do that here at the museum?”

“They do,” Hem said. But he frowned at the empty glass case.

Anna sighed. “Well, that stinks. I was going to write about seeing the Mona Lisa for my school paper.”

“If the painting’s on vacation, I guess you’ll have to take a break, too,” Henry said.

Anna looked offended. “News doesn’t go on vacation.” She turned to Hem. “What else should we see?”

“The Egyptian wing. It’s spectacular.” Hem led them through the maze of the museum to a big hall crowded with statues of Egyptian gods and slabs of stone filled with hieroglyphics. “And look at this.” He led them to a smaller, darker room and pointed to a tattered, wrapped-up something on a shelf in a glass case. “It’s a cat mummy.”

“No way!” Anna stepped closer to read the information card. “I had no idea cats had mummies.”

“All cats have mummies,” Henry said. “Daddies, too.”

Anna rolled her eyes, but Hem laughed as they headed for the European art halls. He seemed relieved to find a Vermeer painting. “Thank God,” he said. “The Astronomer is safe.”

But The Lacemaker was gone. And not far from that empty spot on the wall, two more paintings had been stolen. One was a snowy landscape by Claude Monet. The other was by a painter named Camille Corot. “It was a sailboat,” Hem said. “A really spectacular one. The sky behind it was all moody.” He looked at the empty places on the wall and lowered his voice. “I have this weird feeling that Vincent Goosen and I have the same taste in art.”

José nodded slowly. “Like Harry Potter and Voldemort. They’re on opposite sides, but there’s this weird connection, and in some ways they have a lot in common.”

“Goosen was a society member once,” Anna said thoughtfully. “You really think he’s stealing his favorite stuff?”

“I do,” Hem said. He took a deep breath. “And I have an even worse feeling that he’s not quite finished.”

“Why do you say that?” José asked.

Before Hem could answer, an alarm sounded, whooping through the gallery. It was so loud Henry thought it might shatter the glass cases.

“Attention, s’il vous plaît …”

“What?” Anna shouted over the blaring alarms.

As if he’d heard her, the man on the loudspeaker repeated his message in English: “Attention please, visitors. Due to a security breach, we must evacuate the museum. Please proceed to the nearest exit immediately.”