“Even the best grown-ups can be weird,” Tommy said as he and Calder trudged toward Harper Avenue. “Like Ms. Hussey just said, you think you know them and then you don’t. She was definitely acting funny.”

Calder nodded. “Sometimes my parents seem angry or unfriendly, and then I find out they’re just worried.”

“Yeah, exactly. So we have to tell the other three about the F-A business. I promised Ms. Hussey we would.” Even though he and Calder and Petra went to the same school, by eighth grade they had schedules that sometimes kept them apart all day.

Calder pulled out his phone and hit Petra’s number.

“Funny you called,” she said immediately, without even a hi first. Familiar with the extreme decibel level in Petra’s household, Calder held the phone away from his ear. “I’m about to meet Early at Powell’s Books. She’s walking over here with her little brother. She has him for the afternoon since her mom’s still at work. Hey, stop that! You can’t have a chocolate milk fight in here! If you spill on Dad’s computer, you’ll be in trouble for the rest of your lives!” Calder and Tommy then heard a muffled, “NO, you can’t come this time, we’re having a meeting.”

“Seems like Petra hates being the babysitter,” Tommy said, after Calder ended the call.

“Yeah, the other kids are even more of a handful, now that they’re big,” his friend said. “I used to envy her having all that company, but not so much lately.”

Tommy called Zoomy as they headed for Powell’s. He was back home, and said he was studying the envelope of pictures and reading about the museum. Both could picture him working his way through the art, his nose inches from the page. He’d be back in Hyde Park the day after tomorrow.

“He sounded kind of sad that he’s not here now,” Tommy remarked to Calder as they pulled open the door to Powell’s.

The store was a maze of narrow passageways between old, wooden bookshelves that reached to the ceiling. Ladders squeaked and leaned; footstools were dragged into corners for comfortable browsing or a subdued chat. Employees never glared at kids and left customers alone unless they asked for help. Aside from the rattle of old fans in the summer and the clank of radiators in the winter, the place was quiet — a treasure trove for those who liked hanging out with the printed word, which most people in Hyde Park did.

Both Tommy and Calder had delivered books for Powell’s in the past, but neither were big visitors. Petra, on the other hand, was always stopping by on her way to get groceries for her parents. It was her home away from home. Sometimes she started a book there, left a hidden bookmark, and returned again and again until she’d finished it.

Stepping inside, Tommy and Calder heard Petra before they found her.

“Here’s the book of Sarah Chase Farmer’s ideas, Early,” she was saying. “The one I found this morning. This has much more than the museum booklet Mrs. Sharpe gave us. You’ve gotta hear some of this.”

Then they heard a shrill, “Earl-ee! Earl-EEE!” Rounding a corner, the boys found Petra next to Early and her little brother, who looked like he was about six. Jubie wasn’t about to let the girls talk, at least not yet.

“Hi, guys.” Petra nodded in their direction. “Almost ready here.”

Scanning the shelves, Early crouched next to her brother. “We’re looking for picture books. Just for you, Jubie. Exciting ones, so you can be busy while we’re busy.”

“Yeah, I want crimes. Gangstahs. Pow!” he roared.

“Shhhh …” Early said. “You know Dash and Sum don’t like those books. How about books on digging machines?”

“Tough guys! Pow!” Jubie shouted.

Petra tried to help. “Hey, Jubie,” she said. “My brothers like these books over here. There’s a ton on people doing hard stuff, like climbing mountains, scuba diving, blasting dynamite holes in rock to build roads …”

“Boom!” Jubie appeared satisfied. “With weapons!”

Early sighed and shrugged. “This might not work,” she said to the other three.

“Who are Dash and Sum?” Tommy asked.

“Our parents,” Early said. “We say that instead of Dad and Mom. And hey, this is Jubie. Jubie, meet Calder and Tommy.”

“HI!” shouted Jubie. “Our family writes Dashsumearlyjubie inside our spesh-all books,” he said, bobbing his head like mad. “It’s looooong! And I can write my full name superfast, Ju-bi-la-TION!”

“Great,” Tommy said.

“Good for you,” Calder added.

“He thinks he likes scary stuff more than he really does,” Early said behind her hand.

“Gaangstahs! Now, Early! Not this construction book!” Jubie began to bounce.

Just then a man poked his head around from the Folklore section.

“I like tricky stories, too,” he said to Jubie.

The man’s face had sad lines but also a sparkly smile. Early noticed bluer-than-blue eyes and dark curls. He had a black leather jacket and a soft hat that looked familiar.

“I’ll read you something,” he offered. “How about, hmmm, oh look: The Real Mother Goose. Ever hear of that?”

Jubie shook his head violently. “That’s for babies!”

“Wait!” the man said quickly. “It’s really not. Ever thought about going to sea in a boat that’s too small or getting stuck on a shelf because you can’t spell? Running away from someone with a knife? Falling from a great height? Uh-oh, Humpty Dumpty looks terrified! I wouldn’t want to be on that wall, either.” The man was now on the floor, flipping through pages.

“Okay, let’s get to the dangerous part,” he said as Jubie leaned closer. “Now see, these guys look kind of like bad guys. And oh, boy, this kid is on his own! And the dogs are barking, which usually means trouble.”

“Uh-oh,” Jubie agreed. “But those guys won’t break stuff or hurt the doggies.” He popped one finger into his mouth.

“We’ll find out,” the man said.

Early watched them for a moment, hesitating, and then told Jubie she’d be over in the corner with her friends. Jubie nodded and the man looked up with a quick smile, as if to say, We’re fine.

“Look, something bad’s coming.” The man now seemed as absorbed as Jubie. “Animals are smart. See, they’re trying to get the right people to pay attention.”

The four older kids sat on the floor in the Art Criticism section, where they could keep an eye on Jubie. “Okay, tell us Ms. Hussey’s message first,” Petra said. “Then I’ve got something pretty cool here.” She waved a small red book in the air.

Tommy spilled what Ms. Hussey had said about Mr. Chase’s friendship with Mrs. Sharpe, the Farmer Museum’s choices, and the F-A puzzler.

“Yikes,” Petra said. “Poor man, that’s horrible. So frustrating.”

“Could be the name of the museum,” Calder suggested. “Or a person’s initials.”

“How about a publication like Farmer’s Almanac?” Early said. “I’ve seen that in libraries. Or Flying Aces — they were fighter pilots in World War Two. Oh … I don’t know.” Early broke off happily, just glad to be part of a group of kids her own age, kids who seemed to have had adventures that were as scary as hers and didn’t mind sharing doubts or strange ideas.

Calder was scrolling on his phone. “Functional Acknowledgement,” he read. “Means an electronic acceptance.”

“Whatever.” Tommy glared at his friend. “It could be a place. I have an aunt in Fayetteville.”

“There’s Fayyu¯m, in Egypt,” Petra added. “One of my grandmas lives near there.”

“Or maybe it’s part of a word. A not-polite one,” Tommy said, looking around. “You know, old people get nutty sometimes …”

Early said, “Maybe it was something personal that Mr. Chase needed to tell Mrs. Sharpe, especially since they were friends who’d had a squabble. I hope all the other trustees do show up tomorrow at the museum; it’ll be good to see what they look like, now we know they’ve been fighting.” She giggled. “Somehow, it’s funny to picture old, rich folks whacking each other with canes.”

In truth, the whole disagreement seemed silly to Early, who understood that having enough money made many problems go away. These were rich people fighting over rich things. There was something about Mrs. Sharpe, though — Early understood her determination, and knew that having a mission was important to keep you going, especially when things were hard. Mrs. Sharpe might be wealthy, but there was also a part of her life that was sad.

Tommy sucked in his cheeks, picturing the trustees fencing. I knew Early was awesome, he thought to himself.

“How about the old folks have a pillow fight?” he suggested. “Then they’d just get feathers stuck in the wrinkles.”

“Gross!” Early laughed. Tommy thought he’d never felt so happy.

“My dad said it’s been gruesome at the Farmer for ages now.” Petra’s voice was serious, bringing them back to business. “Some of the trustees were interviewed in the news. Each one is convinced he or she knows what’s best here, both for the city of Chicago and the art. My dad says they know what they’re doing when they talk to reporters, and have tried to use publicity to pressure each other. Those folks each want what they want and — my dad says this is a biggie — they don’t have all the time in the world. He says some old people don’t care what anyone thinks, not anymore. And in this case, they’re old people with lots of power over world-class art.”

“But less power over it once the art is stolen,” Early pointed out.

“You mean, they’re all suspects,” Calder said slowly.

Early frowned. “Not exactly. But I see what you mean: If you steal the art, that means someone else can’t move it.”

“Or else it gets very easy to move — only not in public,” Petra pointed out. “Either side could have done it.”

Calder scratched his head with the M pentomino. “My parents said old people with money can be very ruthless.”

Tommy suddenly remembered Mrs. Sharpe hitting the sofa with her fist. Ruthless … he’d thought of that word, too.

“Like Mrs. Sharpe,” Tommy blurted. “I can picture her stabbing someone, can’t you?”

Petra elbowed him. “You’re a freak, Tommy.” For all Mrs. Sharpe’s bark, Petra couldn’t imagine her hurting anyone.

Early wasn’t so sure. She definitely sensed that being on Mrs. Sharpe’s bad side was a bad place to be. The old woman had been hunting her husband’s murderer for years now, and without much help from the police — someone like that had to be both tough and tricky.

Calder stirred his pentominoes and now pulled another one from his pocket. “Perfect. M for money and F for fight. And Mr. Chase’s F.”

“F for freak,” said Tommy, his words ending in a ghastly squeak.

“Ferocious,” Early added.

“And Mr. Chase is part of Mrs. Farmer’s family,” Petra mused. “He must feel extra bad. This little book, The Truth About My Art, is packed with ideas his great-aunt had about her art and her home. It sounds like she was an awesome person — I wish I’d met her! She’s like a much less spiky Mrs. Sharpe.”

Tommy tried to imagine what a less treacherous Mrs. Sharpe would be like.

He couldn’t picture it.

“Listen to this.” Petra opened the book. “Here’s what Sarah Chase Farmer says about Vermeer’s The Concert.” She read the passage aloud:

“Three faces, two of which are unselfconscious and absorbed, making music in the light. One is forever hidden, but clearly a part of the trio. Because his face is hidden, the viewer returns to thoughts of him again and again. Without a face to decode, the viewer feels a touch of anxiety. Perhaps that is part of Vermeer’s spell: He wants you to worry about what might be coming. He wants you to wonder, What if he turns?

“It’s the story of life. We never see all that we know is there. Art keeps us wondering, and while we wonder, we’re not alone.”

Early looked sad. “That’s haunting. I kind of know what that feels like,” she said. “What if he turns?” Instinctively she looked over at Jubie and the man. Neither of them turned.

Calder thought of the thieves who’d stolen the paintings from the Farmer. They must have felt the same way about the sleeping guard. What if he turns?

Tommy wondered if the man with his back turned had some reason he didn’t want to be seen. Maybe he had an adult-sized Krakatoa, and Vermeer didn’t want to paint it.

Petra was still reading. “Whoa,” she said. “It sounds as if Mrs. Farmer knew what it was like to have hard times. Here in the introduction, written after her death in 1924, it says that she lost her only child when he was a baby and that her husband died suddenly in 1898, just as they were about to begin construction of the museum. She’d inherited a ton of money from her father, who was in the Chase meatpacking business. The museum was opened to the public in 1903, and Mrs. Farmer lived in an apartment on the top floor. The rest of her life was devoted to enjoying and sharing the treasures that made her happy, and to writing this book, which was published in 1930. I’ll bet she loved doing that.”

Even as she said it, Petra wondered if this was too easy. Then she reminded herself that art had once made her feel happy and filled with dreams. Not much lately, but once — when she was younger. When she wasn’t thirteen.

Shoving these thoughts away, she went on, “You guys — what Mrs. Farmer says could be giving us clues about where the art has gone. Especially if the person who planned the theft knows this little book. Like the trustees, right? I’ll come back here with my notebook.”

Early saw signs of restlessness in Jubie and knew she’d have to leave. “Read us some more, Petra. Quick, before I have to take Mr. Pow-Gangstahs to the playground.”

She’s one of us, Tommy thought happily.

“Okay. How about this,” Petra said.

“Welcome to my collection. I truly hope that it will give as much to you as it has given to me. While living with great art is one of the deepest privileges a person may have, I do believe that one only needs to meet and fall in love with a masterpiece in order to call it one’s own. In this way, what’s mine can become yours.

“The people in my art are my friends and family. They speak, filling my life with their presence. I respond. I love to think that others may visit my home and do the same.

“What you see will be different from what I see; a thousand people can love the same painting in a thousand ways. Such is the cycle of life, as art reaches out beyond the will of its maker or owners.

“Great art will live, given a chance.”

“Bit nutty-bananas,” Tommy commented.

“Not if you’re truthful with yourself,” Petra snapped. “And not to someone who loves art and might feel a bit lonely. This is generous and honest. She’s a guide. Lots of us who look at art think about stuff like this, but who says it? And maybe by believing the art could talk back to her, that it was kind of alive, she made it happen. Maybe what she says in this book can change the people who read or hear it. Maybe there’s some magic here. Some power. Just like athletes before a big game psych themselves into winning, you know? They focus extra hard on what they want to see happen because they believe that’ll change what they can do. Why is that nuts?”

Tommy gazed at the shelf behind Petra’s head, hoping one of the titles might help him. “It’s not — it’s the good kind of nuts. Like ours.” Calder elbowed him in the ribs and Tommy stared back furiously when he realized why. I hate hanging around with girls. Seems like everything gets twisted into something embarrassing.

Early, happily, didn’t seem to notice. “I don’t think any of Mrs. Farmer’s ideas are wacky,” she said. “It’s the opposite — they’re more than right! But what I don’t understand is, who would steal from a museum like this? I know we said stuff about the trustees taking the art from each other, but the truth is that a theft like this would be done by someone pretty bad, right? I mean, who takes priceless art like this? Are we sure it’s safe for us five to be working on it?”

“Mrs. Sharpe wouldn’t pull us into something really dangerous,” Petra said, although she didn’t look positive. She glanced around and then added, “I don’t think. And Ms. Hussey would know if it was something we shouldn’t be doing. I think.”

Early rolled her eyes unhappily just as Jubie popped to his feet and trotted over. “All done, Early. No puppies got hurt.”

When Early turned to thank the man who’d been reading to Jubie, she found he was already gone. Another man in a black leather jacket, someone younger and scruffier, was running his finger along the titles in a nearby aisle.

“Hey, black jackets are big around here, aren’t they?” she half whispered to her new friends.

Sliding the slender red volume back onto its shelf, Petra shrugged. “Haven’t noticed.”

A shadow crossed Early’s face. As if reading her mind, Tommy said, “Make you think of blackbirds baked in a pie? Next thing we know, someone’s nose will get snapped off.”

Calder elbowed Tommy, knocking him sideways. Jubie imitated the two big boys, staggering sideways into a shelf.

“Yeah, snapped off!” Jubie shouted. “No nose!”

Early bent down to pick up Jubie’s hat, then grabbed his hand. “See you,” she said — mostly to Petra, and a little to the boys. She was out of the store before they could say good-bye.

“You scared her,” Calder said to Tommy.

“I don’t think so,” Petra said. “It was like she saw something.”

The three scanned the area Jubie and the man had been sitting in.

“No one,” Calder said. They walked through the bookstore together, even ducking under water pipes in the basement to check out Mysteries and Science Fiction, but they couldn’t find even one black jacket.

“Doesn’t mean they’re not here. This is an easy place to change directions and hide, there’re so many loops,” Tommy said, thinking of Goldman and his underwater palace.

Before leaving, Petra muttered, “I wish I could take Mrs. Farmer’s book home, that it wasn’t so expensive. It’s twenty-five dollars. Wait, just a last look,” and stepped back to check the shelf.

The others heard her gasp.

The book was gone.