"Eureka!"

Startled, Fortuna nearly pitched forward into the grand piano she was perched on.

Flavia was framed in the doorway to the stairwell of the Shrieking Shack, holding a beaker of electric blue liquid aloft in both hands.

"Eureka," she said again, reverently lowering the container. "What are you doing?"

"Tuning the piano without—" She caught herself. "Magic. With a wrench."

"But nothing to tell you what pitch you're hitting?"

Fortuna looked down at the piano's insides, at the parchment jammed between two of the strings that were responsible for middle C. She'd been at it for twenty minutes. "I'm starting to think I may be tone deaf," she said reflectively.

"I'll ask Feely for a spell that will keep it tuned," Flavia said. "She won't tell me willingly, so I'll poison her and hold the antidote hostage. Do you play?"

"No, but I'd be good at it if I learned, so we should make sure it works." Fortuna gestured at the beaker. "What did you find?"

Flavia raised her discovery once more. "The substance we discovered in the Gryffindor common room on Tuesday morning is dog hair. Since students may only have an owl or a rat or a cat or a toad, we can deduce it wasn't left by a student. Who was in the common room that wasn't a student? Sirius Black."

"But what can it mean, Holmes?"

"It means, Watson, that Sirius Black—" Flavia consciously paused for dramatic effect. "Has a dog."

"We have a dog," Fortuna said.

Behind her, the sound of Alexander devouring his fourth steak and kidney pie of the evening stopped.

The two girls looked at him. Noticing their stares, he started wagging his tail.

But even canine antics couldn't distract Flavia from the disappointment. She groaned. "We do have a dog, and this is just his hair."

Fortuna sympathized. It had been too much to hope that everything was going to fall into place with the simple application of a few gray cells, but their complete lack of progress was dispiriting. Four days had elapsed since Sirius Black's brief appearance, and their only real clue had just proved to be a red herring. She'd known better than to actually believe they would find secret passages hidden within every cupboard, that leggy dames who knew too much would walk into their office, or that a priceless treasure hidden in an ordinary statue would fall into her lap, but she had expected a little bit of progress by now.

"We could make a list of suspects," Fortuna suggested.

"Using what evidence?" Flavia asked, sounding morose.

"Well, we know it's someone at Hogwarts because the Fat Lady confirmed that he knew the password," Fortuna said. "That narrows the suspect pool down from 'anyone in Wizarding Britain.'"

Flavia agreed, and they went upstairs to their lab. Fortuna suggested they brainstorm and transfigured part of a wall into a chalkboard.

The first name Flavia wrote was that of Professor Binns.

"The obvious suspect," she declared.

Fortuna arched her eyebrows. "There's no evidence to say that he did it."

"Precisely," Flavia returned. "As a ghost, he leaves no evidence anywhere at all."

"That's logically unsound," Fortuna said.

"Well, perhaps, but we can't rule him out. Absence of evidence is not evidence of absence, at least not when the absence is the evidence. Besides, it's never the obvious suspect."

Fortuna doubted this was logically sound, either, but didn't feel like untangling it. It wasn't as though she knew enough to truly rule anyone out. Still, surely there were more likely suspects?

"Remus Lupin," she suggested. If he was concealing something that the majority of people thought should get him fired, what else might he be capable of hiding?

She had spoken without thinking, and found herself wondering how she could justify her suggestion without breaking her promise not to reveal that he was a werewolf.

But Flavia didn't even hesitate. "Excellent," she said. "The Defense Against the Dark Arts position is supposedly cursed, so people who aren't desperate or stupid or evil don't take the job. One of them was actually You-Know-Who in disguise, or something like that. It was Daffy's first year and the rumors were hard to sort out."

"Cursed?" Fortuna asked. "And nobody's broken the curse?"

"It wouldn't be a cursed position if someone had broken the curse."

Unlike her analysis of their History of Magic professor's guilt, this was logically sound. "Has anyone tried to break the curse, then?"

"Well, I suppose someone must have tried before. The Board wouldn't just let a teaching position be cursed for years if they could help it. And Dumbledore is a very powerful magician in his own right—if he could have fixed it, I'm sure he would have by now."

Idly, Fortuna wondered what the headmaster had missed.

A cursed object, hidden by You-Know-Who in a room accessible only to those who were desperate to hide evidence. A shabby tiara, openly placed among tens of thousands of abandoned things, exposed only on occasion to people in a hurry to get rid of something and get away.

Hiding in plain sight.

Fortuna thought about her strategy with the study group.

Dumbledore wouldn't find out, and he'd continue to lose defense professors to scandal, injury, illness, and death. It was possible for her to stop it, though she felt annoyed with herself for even considering the possibility. It was his job, not hers.

But what about the people affected? Did Professor Lupin deserve to suffer a possibly deadly mishap because he'd taken the only job he could get? Did Angelique deserve to grow up without someone to teach her how to fend off basic magical household pests? Did she want to deal with the disruption to her plans for her classmates that the inconsistency of teaching quality would cause?

There was only one answer.

"Well, in that case, we'll have to keep a closer eye on him," she said, mentally resolving to break the curse when she got back to the castle. If they made it back by four, she'd have enough time.

"And Minverva McGonagall," Flavia added. "Nobody would question her presence in Gryffindor Tower, and she was the first teacher on the scene."

Severus Snape naturally followed. It was easy to cast the slick-haired professor as a villain, as he was exactly the kind of dodgy person who would cavort with cloaked individuals in shady bars. The mere mention of his name roused Alexander's hackles, another sure sign their professor was somehow involved.

Flavia rounded out the first column with "Another Professor." A bit generic, but it captured the fact that every professor had the means to assist a serial killer breaking into Hogwarts.

She hesitated a moment, then wrote down the names of Ophelia and Daphne de Luce.

Fortuna folded her arms.

"What? You saw how Feely was that night! They're both menaces. You don't know them like I do. They're like crazed badgers."

Fortuna allowed her friend's rant to wear itself out before she got back to the list, adding Filch and Hermione Granger.

"Not Filch. He's the butler, can't have done it. That cat of his, though…" Flavia trailed off. "Who's Hermione Granger?"

"Aside from the fact she's a Gryffindor and is therefore the only student on our list who could have let Black in, she's one of Harry Potter's friends and could provide access to him."

Flavia considered this argument, then wrote Candidus Craven beneath Hermione's name.

Fortuna agreed. If anyone in their friend group harbored traitorous intentions, it was definitely Candidus.

Schmuck.

The last names were the Weasley twins and the Fat Lady, based on the fact they were the only witnesses—the only real witnesses. Gryffindor Tower was filled to the brim with students who were eagerly boasting about their brush with death, but cursory interrogation revealed that none of them had even been aware of Black's arrival until the deputy headmistress was rallying them for a headcount.

The Fat Lady played up her adventure as well. Evidently, spending one's existence glued to a wall did not make for entertaining fare, and she milked the tale for all it was worth. This proved not to be much; though able to perform her job out of instinct, she had been sleeping off a bottle of merlot she'd shared with a knight from the fifth floor.

Only Fred and George Weasley had managed to see the man, though they hadn't even realized who he was before he was gone. They had been working on an invention when he entered, and he'd bolted immediately on seeing them. The most they could say was that they were pretty sure he'd been wandless.

There was nothing really to go off of there, so their best bet was to tackle their list of suspects. Gather more evidence, perhaps do a little bit of stalking, ransack their rooms for clues, and figure out a plan of attack.

But not tonight, she thought, sitting down on a corner of the bed and kicking her shoes off. She was exhausted after all the detentions with Filch, an exercise in gruntwork and wasted time she hoped she would never experience again. They'd scrupulously followed the detentions with nightly trips to the Shrieking Shack, lest the Veritaserum go neglected or Alexander starve, so she hadn't gotten more than four hours of sleep a night.

Flavia had already started to drift over to her potions table, and Fortuna settled into the blankets. It was already almost one, and she'd need a nap if she wanted to destroy the tiara before Dumbledore woke up and be able to make it through their Saturday study group meeting.

It felt like she'd been walking for hours. She was back in the hospital, walking past white rooms through white hallways under white lights. Everything bright, sterile, painful to look at.

Finally she stopped at the foot of a girl's bed. Skin sagged off her body and the pallor of death lay over her like a blanket. The girl's lips moved but there was no sound. Her lips slowed and her body stilled aside from labored breathing, assisted along by two tubes running up her nose. She reached forward and reached forward and—

The girl's face split open in a dozen different places, and bark sprang up between the cracks and spread, replacing her flesh. The transformation spread down her body and one of her arms lengthened. It slithered, vine-like, around her thighs and fused to her legs. Her other hand merged with her cheek, leaving her face half-covered.

There was no way to dislodge that hand, nothing for her to do but scream.

Fortuna opened her eyes.

Alexander was looking at her with an expression she could only call concerned. She saw that her arm was dangling off the bed, and that he was nudging her hand. Waking her up.

She slid out of bed and wrapped her arms around him, resting her cheek against his shoulder. His fur smelled like daffodils and nightshade, courtesy of the anti-flea shampoo she and Flavia had concocted.

The attack on her parents, the extinction of her native language, her memory loss: she'd subconsciously been assuming they were the result of a magical accident. If she could figure out how magic worked, she could figure out how it had happened.

She'd been wrong.

Someone did this on purpose.

She tried to remember details from her dream, any faces or words that could give her a place to start, but all that remained was the conviction that someone had deliberately created the monsters in a controlled environment. If Alexander hadn't woken her up mid-nightmare, she wouldn't even have that.

No. No need to frame it like that. Progress was progress. Three weeks ago, she'd known nothing. Now she had a starting point and a number of clues, each pointing to something bigger and more sinister than the last. A malevolent intelligence seemed to be at work, and she would need to approach that with patience and caution.

She could do that. She could do anything.

"Thank you," she told Alexander.

"Hm?" Flavia asked. She was bent over a cauldron.

"Nothing." Fortuna got up and went over to see what her friend was doing. "What are you working on? I thought we didn't have to do anything else for the Veritaserum."

"Poison," Flavia said, drawing out the word with relish. "For Ophelia, of course."

"Of course," Fortuna said automatically. "We should be getting back. It's past three."

Flavia rolled up her sleeve and looked at her wrist. Then she looked at Fortuna. "How do you tell time without a watch?"

"By the position of the sun," Fortuna said, preparing to take point. They'd need to avoid a prefect, Professor Burbage, two seventh-years, Mrs. Norris, Peeves, and an entire congress of ghosts to make it back without getting caught. "Come on. Maybe Black is back in our common room."

It turned out that Black was nowhere to be seen, but Flavia was tired enough she wasn't disappointed. Fortuna watched her go up the stairs to their dorm and continued to watch the stairs after she'd disappeared, waiting.

Two minutes later, Harbinger appeared. He'd come to associate Flavia's nocturnal return with hers, and he had deduced her presence down here from her absence up there.

She grinned as he trotted down to greet her, tail and head held high. He was so smart, she thought as she picked him up and ran a fingernail along his vibrating throat. He was the smartest cat in Hogwarts—

Hermione's cat was smarter. Annoyed, she prodded her power for a better, more correct answer. After a few moments, she was able to console herself with the fact that this Crookshanks was only half a cat.

And Harbinger was a whole cat, a complete cat, a perfect cat. He was undeniably the handsomest—

Most people would agree that Kenneth Towler's calico Artemis Loudmouth was the most attractive of the Hogwarts feline population. Then there were Farfallele, a tuxedo cat who sported a white bowtie-shaped mustache, and Catacadabra, a long-haired, squash-faced Persian that people inexplicably admired despite the fact that she was a long-haired, squash-faced Persian.

As Fortuna went down the list of purebreds, tabbies, and tortoiseshells, she realized that only she had the appropriate respect and regard for sleek gray cats. In a Hogwarts beauty pageant, Harbinger would come in forty-nine of sixty-one, and he was only that high because he was still a kitten and that boosted his perceived cuteness. As an adult, he would rank fifty-three.

Deeply offended, she took her hypothetically slighted cat to a couch and contemplated the wisdom of not asking questions. He wriggled out of her arms and started sharpening his claws on the cushion next to her, indifferent to the benighted rabble that surrounded him. Fortuna commended him on his nobility and magnanimity, then rooted through a bag a second-year had left in front of the fire for a quill and piece of parchment.

Harbinger batted at the quill and she teased him for a few minutes.

She was dithering.

She triple-checked that nobody else was around and finally brought herself to write a single sentence.

My name is Fortuna Floris and I have a superpower.

She put the quill down, folded the parchment into a little square, and tucked it in her pocket.

Now she had something that needed to be hidden.

Step two was to go to the seventh floor.