"The cobblestones that you stole?" the inspector said.

She sighed, realizing that what she was about to explain to this incompetent man was going to fly directly over his head. "No one is stealing cobblestones," she explained. "And they aren't simply disappearing. They are falling."

"Falling?" said the inspector. "Cobblestones don't fall from the ground. What do you take me for? An imbecile?"

Oona nodded. "For once, you are right, Inspector." The inspector guffawed, but Oona continued before he could protest. "Do you have a coin?"

"A coin?" he said. "If you are hinting that you would like to run off and buy yourself a treat, then you are sadly mistaken. I do, however, have a hard candy in my pocket, if that would satisfy."

Oona nodded enthusiastically that it would indeed satisfy, and from his pocket, along with a jumble of keys, a handful of pocket lint, and a used handkerchief, he produced a round candy in a wax wrapper. Oona took the candy, careful not to touch the pocket lint or the used handkerchief.

"Thank you very much," she said, and dropped the piece of candy into the hole where the cobblestone should have been. There was a moment of silence before a soft, echoing pat sound drifted up through the hole, as if the candy had hit something not too far below the street.

"You ungrateful little juvenile!" the inspector said. "That was a perfectly good piece of candy."

"But do you see?" Oona asked.

"What I see is that you are a menace," he said, "and that I have a good mind to arrest you for littering." His nostrils flared, and Oona thought for a moment that he might actually do more than threaten.

It was Isadora who saved her when she shouted at them from the carriage: "Why are you two lack-wits arguing about potholes when you should be finding my mother's dresses? Or have you forgotten that the Midnight Masquerade is tonight?"

Oona straightened, intent on telling Isadora-in as rude of terms as possible-exactly just what she could do with her mother's dresses, when several thoughts suddenly clicked in her mind, like pieces of a puzzle locking together.

She looked from the pothole at her feet to the museum, and then from the museum to Madame Iree's Boutique for Fine Ladies next door. Most of the buildings on Dark Street were pressed together, wall to wall. As Oona had observed only the day before, the dress shop was no exception. On one side was a handbag shop, and on the other side was the museum, with the dress boutique looking rather squashed in between.

"Isadora," Oona said, her heart rate beginning to rise, "is your mother's shop open?"

Isadora shook her head. "Mother was too distraught to open the shop today. And besides, she's been too busy at home trying to st.i.tch together new gowns to make up for the stolen ones."

Oona remembered something that Madame Iree had said the day before: how the dressmaker would love to get her hands on some turlock root, so she might age backward and wear the dress made of glinting cloth.

"Do you happen to have a key?" Oona asked hopefully.

"Just so happens that I do," Isadora replied. "But the dresses are all gone, except for the small, pretty one in the window. You'd never fit into it ... and anyway, I told you yesterday, Mother makes dresses only for students of the academy, or-"

"Or alumna," Oona finished for her. "Yes, I know. But I think I might know who the thief is." And more important, how they got in, Oona thought. "I need to see inside the showroom to be certain."

"Very well," Isadora said. "If it will help get my dress back. But this better not be a waste of time."

Wearing a ruffled pink dress with lacy white trim, she stepped down from the carriage and handed the driver several coins. Meanwhile, Oona returned to her own carriage, leaving the inspector standing in the street, scratching at his wiry black hair and staring down at the pothole. Oona removed the hatbox from the carriage, peeked inside to make sure that the toad was all right, and then handed the box up to Samuligan in the driver's seat.

"Keep good care of that, Samuligan," Oona said. "And wait over there, at the curb. Deacon, with me."

Deacon leaped to her shoulder and the two of them met Isadora in front of the giant top hat.

"Should we bring the inspector?" Isadora asked.

Oona looked back to find the inspector with his arm stuck shoulder deep into the pothole, no doubt attempting to retrieve his candy.

"I believe we will do just fine on our own," Oona replied.

It's gone!" Isadora shouted.

"What is g-" Oona stopped herself short, realizing all too quickly what Isadora had meant by "it."

The three of them, Isadora, Oona, and Deacon, stood in front of the dress shop. Isadora had just inserted her key into the lock when she looked into the storefront window, only to discover that it was empty. The glinting-cloth dress was gone. Isadora looked pale.

"Perhaps your mother took it home," Oona suggested.

Isadora shook her head. "No. That can't be. I was just on my way to fetch Adler from the Magicians Legal Alliance. Mother wanted us both home to help her sew the replacement dresses that she has been working on all night. On our way back home, I was supposed to stop by the shop and take the glinting-cloth dress home, for safekeeping."

"Your mother didn't take it with her when she left yesterday?" Oona asked.

Isadora gave her a look like she was very stupid. "No. Aren't you listening? Mother was so distraught when she left yesterday that she forgot all about it. That's why she gave me the key to pick it up today."

Oona had a vague memory of seeing the dress in the window on her way to the Goblin Tower that morning.

"Come, Isadora," Oona said. "If we're going to find any of these dresses, we need to go inside."

They closed the door behind them, and Oona found the first room of the shop much as she remembered it: the tables and the empty teacups, the red-and-gold-striped wallpaper, and the scent of lavender potpourri. The missing dress from the front window seemed to be the only difference.

Oona quickly moved to the showroom in the back, Deacon clinging tightly to her shoulder. The door stood wide open. This room, too, was as she remembered it: the naked mannequins and the crystal chandelier, the ever-burning lamps and the raised platform for dress alterations. Except, no ... everything wasn't the same. The mirror that hung on the wall in front of the platform-it was now cracked down the middle and hung slightly crooked. It reminded Oona of seeing Inspector White straighten the mirror on the wall only the day before. And there were several other differences. One of the mannequins beside the platform was lying on its side, and in the center of the room, where only one white candle had been lying on the floor, there now lay two.

"How do you suppose the thief got in and out?" Deacon asked.

Oona walked to the middle of the room and looked up at the chandelier. Two of the candleholders were empty. Isadora gazed down at the two candles on the floor.

"That happens all the time," she said. "The candles keep falling out of the chandelier's holders. It's a complete nuisance because we keep having to put them back up, and Mother won't allow us to actually light the candles since she's afraid they will just fall and light the dresses on fire. It's too bad, too, because candlelight is far more flattering than those magic lamps."

Oona smiled. "I suspect that the reason the candles keep falling is because Mr. Bop lives up there." She pointed to the ceiling.

Isadora's face scrunched up, as if she did not understand ... but then her expression brightened. "Oh, you mean that great big fat man? I've seen him."

Oona nodded, remembering how the floor at the Magicians Legal Alliance had shaken quite noticeably whenever Mr. Bop had moved. "Indeed. Mr. Bop is so enormous that when he walks around up there, he causes the ceiling to shake, which in turn rattles the candles out of their holders."

"So what does that have to do with the stolen dresses?" Deacon asked.

"So far as I can tell, absolutely nothing," Oona said. "But that mirror, on the other hand, I think has quite a bit to do with our mystery. It was not cracked yesterday, that much is for sure. I remember watching the inspector admire himself in its reflection as he straightened it on the wall. Also, look at that mannequin next to the platform. It was not lying over on its side like it is now. I'm quite certain."

"I believe you're right," Deacon said, gazing down at the toppled-over mannequin. "All the mannequins were upright yesterday."

Oona looked around the room, letting her eyes roll where they would. The floor was wood, polished to a brilliant sheen and flawless.

"The door appears to be the only way in," Deacon observed.

"Appears," Oona said.

"What is that awful smell?" asked Isadora. "Is that your bird?"

"I beg your pardon?" Deacon said, puffing up his feathers.

"No, wait," Oona said, and sniffed the air. "Isadora is right. This room has a distinctively different smell than the room out front, with its lavender potpourri."

Deacon began to sniff as well. "It has an earthy, herbal smell."

"With a hint of cinnamon," Oona added as she followed her nose across the room to one side of the raised platform, where she found what at first appeared to be a random piece of dirty black cloth on the floor. She held up the cloth to reveal a flimsy black dress. Upon closer examination, Oona found that, like her own dresses, this one was fitted with little hidden pockets. She reached inside one of them now and brought out a small metal canister.

"Perhaps the odor we smell," Oona said, "is that of the so-called Witchwhistle Beauty Cream?"

She twisted the top off the canister and the smell that came out was quite powerful. She needed only a glimpse of the green jellylike substance inside to know that it was the same stuff she'd seen caked on the young witch's face the night before. Oona quickly closed the canister and put it back in the black dress's pocket.

Deacon sniffed. "By Oswald, it is the same smell! And isn't that the dress belonging to the young witch, Sanora Crone?"

"Indeed," said Oona.

"But what is it doing here?" Deacon asked.

Oona nodded. "Good question, Deacon. She must have left it behind for some reason. But why?"

Isadora looked furious. "You mean to tell me that that dirty little witch is behind this?" She reached out for the black dress, as if she was going to take it from Oona's hands and tear it up. But Isadora's hand stopped short. She pulled her hand back, clearly not wanting to touch the smelly rag.

"I think Sanora is not just behind this thievery, Isadora," Oona said. She flung the malodorous dress over her shoulder before stepping onto the platform and running her fingers along the edge of the cracked mirror.

"What are you doing?" Deacon asked.

"If you look at this building from the outside," Oona began to explain, "you'll see that it is squashed between the handbag shop on one side and the museum on the other. This wall here presses right up against the museum."

Oona gave the mirror a push, hoping that her instincts were not wrong. The bottom portion slid sideways and up like a pendulum, revealing a large opening in the wall behind it.

Deacon took in a sharp breath. "A hole!"

"A hole, indeed, Deacon," Oona said. "It was curious to me why the inspector had needed to straighten the mirror in the first place. Now we know why. Someone was coming and going through this hole."

Deacon glanced quickly around. "But why is the mirror now cracked?"

"I'm not sure," Oona said. "Could be that the thief knocked that mannequin over today when returning for the dress in the window. The mannequin then fell and struck the mirror."

Deacon nodded that it was certainly possible.

Lowering herself to her knees, Oona peered into the inky blackness of the hole in the wall and began to crawl through.

"I'm not going in there," Isadora said.

"You don't have to," Oona called back. "But if I'm not mistaken, then this hole leads ..."

Next door, into the Museum of Magical History," Oona finished.

She pushed aside what felt like some kind of heavy fabric and stood, smoothing out her dress. Deacon hopped into the room before fluttering to the corner of a large wooden desk.

"I do believe we are in the curator's office," Deacon observed.

"Yes, we are," said Oona. "We are in the bas.e.m.e.nt. The steps in front of the museum rise up so high that the bas.e.m.e.nt is actually on the same level as the street ... and, more important, the same level as the showroom next door."

An ever-burning lamp glowed dimly on the desk, its enchanted flame giving the room a greenish tint. A long tapestry depicting an entire galaxy of stars and constellations took up the greater part of the wall behind the desk. It was from behind this tapestry that she and Deacon had emerged. The floor was polished stone. To the right of the desk stood a broken gla.s.s case, above which hung a small bra.s.s-plated plaque. The inscription read: FAY MORS EXPUGNO AND FAY MORS MORTIS.

MAGICAL MIND DAGGERS.

FIRST EVER ACQUISITIONS OF THE MUSEUM.

OF MAGICAL HISTORY.

AUGUST 12, 1418.

Oona moved closer to the room's single door and examined the lock. "Look here. You see, the heavy-duty bolt has a latch on this side of the door, and can only be opened with a key on the other side. Once they took the daggers, the thief unlocked the door and then pushed it open to make sure that no one would go looking for how they actually got in. Everyone a.s.sumed that the thief came in through the open door."

"So the thief entered and exited through the hole in Madame Iree's wall," Deacon said. "But how did they get into the showroom?"

"I think the answer to that has to do with the missing cobblestones out front," Oona replied.

"How is that?" asked Deacon.

Oona didn't answer, but instead she pulled aside the tapestry and crawled back through the hole into the showroom, Deacon following closely behind. They found Isadora standing where they had left her, arms crossed over her frilly pink dress, fingers drumming.

"Did you find the dresses?" she asked.

"Shh, Isadora," Oona said, before removing her father's magnifying gla.s.s from her dress pocket and beginning an examination of the floor.

"Don't shush me!" Isadora scolded. Nevertheless, she remained sullenly silent as Oona conducted her investigation.

It has to be here somewhere, Oona thought. There must be a second hole. It's the only way.

But after several minutes of searching the floor, she found nothing. Not even a single crack. She sat down beside Deacon on the edge of the platform, feeling quite unsure of her theory. She had been so certain that Sanora Crone had come in through the floor of the showroom and then broken through the wall in order to enter the museum.

She stared at the magnifying gla.s.s, thinking of her father, and wondering if he would have been disappointed in her. She wished he was there, beside her. Surely her father would have known what to look for. But he wasn't, and he never would be. She bowed her head, running her fingers through her hair ... and that was when she saw the faint scratch marks in the wood at her feet.

"There," Oona said.

She brought the magnifying gla.s.s to the scratches along the bottom edge of the platform, and Deacon peered through.

"Scratches in the polished wood," he said. "What does it mean?"

Oona hurriedly moved to the other side of the platform, planted her feet firmly against the floor, and pushed.

"Here is where Sanora got in!" she exclaimed.

The platform slid easily across the smooth wood, revealing the secret beneath. Deacon hopped excitedly from one foot to the other, staring down at the hole in the floor. The very top of a ladder could be seen descending into the darkness below.

Isadora looked from the hole in the floor to the hole in the wall. "I don't understand. Why are there two holes?"