Poppy took it better than Rowan expected.

  He'd thought she'd be upset. Or frightened. Or would at least need a minute to absorb the fact that her three friends had spent Saturday fighting venomous arthropods in the mountain passes above the Forbidden Forest. Instead she sat on the grass outside the paddock after Care of Magical Creatures on Monday afternoon, knees drawn up, field guide open across her lap, and asked questions.

  "The matriarch surfaced from underground. How far underground?"

  "Three or four feet. The structural webbing was laced through the soil above her."

  "And the smaller ones were clicking before she appeared. Was it the same clicking as the ones in the trees?"

  "Different," Iris said. She was sitting next to Edmund, who had been silent since they'd started talking. "The ground ones had a faster rhythm. More staccato. The ambushers were slower and they clicked in pairs."

  Poppy flipped to a page in her field guide and ran her finger across a diagram Rowan couldn't read from where he was sitting. "That's summoning behaviour."

  "Summoning what?" Iris asked.

  "The matriarch. The clicking you described before she appeared, that's a different pattern from the one in the field guide. The field guide says thornbacks drive prey into ambush positions, and they do, but that's during a regular hunt. What you're describing sounds like the pack was holding you in place and calling her up at the same time."

  Iris was quiet for a second. "I told them the pack was herding us. During the fight. I was quoting your field guide."

  "That would have been right if it was just the ground pack and the ambushers doing their usual thing. But you'd already killed several of them and burned through their web. At that point the pack had shifted into colony defence, and colony defence means waking the matriarch." Poppy looked up from the diagram. "You're lucky she came up fifteen feet away and not directly under you."

  "I don't feel particularly lucky," Rowan said.

  "No, I mean genuinely lucky. Matriarchs can surface without warning if the prey is standing on the den web. The vibration from your feet would tell her exactly where to come up." Poppy chewed her lip. "The reason she surfaced at a distance is probably because you'd burned through the ground web between you and her chamber. The fire destroyed the precision of the signal. She knew you were there but not exactly where."

  Edmund had been pulling grass out of the ground in short, agitated tufts. "And you're going back."

  "Saturday," Lawrence said.

  "Right. Into the mountains. Where the giant armoured spiders are."

  "We killed the matriarch," Lawrence said. "The pack won't have reorganized."

  Edmund looked at Rowan. Rowan could see him working through the objections and discarding them one at a time because he already knew none of them would land. He pulled out another tuft of grass.

  "I want to come," Poppy said.

  Everyone looked at her.

  "I don't need to be anywhere near the fighting. I want to see the den after the matriarch's gone. A thornback colony restructuring after losing its queen hasn't been documented in any of the field literature. Professor Howan would give me extra credit for the rest of the year." She closed her guide. "Also, your descriptions of the clicking patterns are terrible. I need to hear them for myself."

  "It could be dangerous," Iris said.

  "I know what thornbacks do when they're agitated and I know what they do when they're mourning a matriarch, and those are very different things. A mourning colony retreats underground for days, sometimes weeks. They won't be aggressive." She paused. "Probably."

  "You're not coming past the treeline," Rowan said.

  "I'll stay at the den site. I'll document the web structures while you three keep climbing. That's what I actually want to see." She looked at Lawrence. "I can also tell you what species of flora the thornbacks avoid, which would give you a route that keeps you clear of their territory on the way up."

  Lawrence almost smiled. It was the closest thing to a smile Rowan had seen on him since August.

  Edmund pulled out one more tuft of grass. "If Poppy's going, I'm going."

  "You don't have to," Iris said.

  "I know I don't have to. I'm going."

  Sebastian was waiting in the Undercroft on Wednesday evening when Rowan came down the stairs. He was sitting on the trunk in the corner with his wand across his knees and his legs stretched out in front of him. Ominis was in his chair. Anne wasn't there.

  "You look like you fought something," Sebastian said.

  Rowan's arm was still tender under the sleeve and he'd been favouring it without realizing. "Care of Magical Creatures project. One of the Kneazles bit me."

  "Kneazles don't leave swelling like that. My aunt kept them." Sebastian didn't push it. "Sit down. I want to talk about the championship before we spar."

  Rowan sat on the edge of the duelling platform. The Undercroft was warm and dry and the light from the sconces threw long shadows that shifted when the flames moved.

  "I won the first round," Sebastian said. "Boy from Beauxbatons. He was good but he telegraphed his Stunners and I read his patterns inside the first minute. Caught him with a Disarmer through a feint, same combination we practiced."

  "How did the nonverbal casting hold up?"

  "It didn't. Not reliably. I threw two silent spells in the first match and one of them fizzled. The other connected but the Beauxbatons boy didn't even react to it, which tells me it wasn't strong enough to register." He turned his wand over in his hands. "The second round was a fourth-year from Durmstrang. She was faster than anyone I've ever fought except you and Hecat. She had this thing where she feinted left with her body and cast right, and I kept falling for it even after I'd spotted the pattern because the timing was so tight I couldn't override the instinct."

  "How long did it last?"

  "About four minutes. She put me down with a chain I didn't see building. Body-Bind into a Disarmer into something that felt like getting hit with a wall." Sebastian's jaw worked. "Clean loss. I didn't have an answer for her and she knew it from the second exchange."

  Ominis spoke from his chair. "He's been insufferable about it since August. I told him losing a round at an international championship is a respectable result for a third-year and he looked at me like I'd suggested he take up knitting."

  "It is a respectable result," Rowan said.

  "I know it is." Sebastian stood up and stepped onto the platform. "But the Durmstrang girl was using techniques I've never seen and I couldn't adapt fast enough, and that's the part I keep going over. I want to be faster at reading new patterns. That's what I want to work on tonight."

  Rowan stood up too. He could work with that. They'd spent enough time sparring that Sebastian's combat instincts were sharp, but the tournament had shown him the limits of drilling against the same opponent. He needed unfamiliar sequences. New angles.

  "Throw things at me I haven't seen before," Sebastian said. "Don't be predictable. Don't be nice about it."

  "When have I been nice about it?"

  Sebastian grinned. It was the old grin, the competitive one, and for a moment the weight of the championship loss wasn't sitting on his shoulders. "Fair point. Your go."

  They duelled for an hour. Rowan threw combinations he hadn't used before in the Undercroft, spell sequences built from what he'd watched the attackers do in the shop. Overlapping angles, pressure from unexpected directions, chains designed to force the opponent into responding to the wrong threat. He softened them for sparring but kept the underlying logic. Sebastian struggled with the first few exchanges and then started adapting, and by the end of the hour he was reading Rowan's feints two out of three times.

  Ominis called out adjustments from his chair. "Your left side is open every time you throw the curved Flipendo. Sebastian, you're leaning into your dodges. Stay centred."

  They finished drenched in sweat and breathing hard. Sebastian sat on the platform edge and drank from a water flask and didn't say anything for a while.

  "The Durmstrang girl," he said eventually. "Her name was Katrin. After the match she shook my hand and told me I was the best third-year she'd faced. I wanted to hate her for it but she meant it, and that made it worse somehow."

  "It made it worse because you wanted her to dismiss you," Ominis said. "That would have been easier to be angry about."

  If you discover this tale on Amazon, be aware that it has been unlawfully taken from Royal Road. Please report it.

  Sebastian looked at Ominis with something between annoyance and recognition. "I really wish you'd stop doing that."

  "Doing what?"

  "Being right about things I haven't figured out yet."

  Ominis's expression didn't change but something around his mouth suggested he was pleased.

  Rowan packed up his things. At the base of the stairs he turned back. "Sebastian. The shop attack over the summer. The people who came after me."

  Sebastian's face changed. He'd heard about it, everyone had heard about it, but they hadn't discussed it directly.

  "The magic they used was old. Dark." Rowan looked at Ominis. "One of the attackers used a word to collapse the anti-Apparation ward. Every body in the room, conscious or not, Apparated simultaneously."

  Ominis was very still.

  "I need to know if you've ever heard of anything like that."

  The Undercroft was quiet except for the sconces. Ominis turned his wand between his fingers, a slow rotation, and Rowan could see him choosing what to say.

  "There are old families who pass down certain invocations. They predate modern spellwork by centuries, maybe longer. They're tied to blood and lineage, and they work through the caster's connection to their family line." His voice was careful but he wasn't evading. He was describing something he knew about from the inside. "The Gaunts had them. My father used one once in front of me when I was young. A single word that sealed every door in the manor at once. I remember the feel of it. Something pulling in the air, as though the magic wasn't coming from his wand but from the stone of the house itself."

  "Could you identify which families would have that kind of magic?"

  "Not from a description. The invocations are specific to each bloodline. But one word moving multiple bodies over distance through an active anti-Apparation ward?" Ominis turned his head slightly, an unconscious gesture that oriented his hearing. "That's ancestral magic. Pureblood, almost certainly, and one of the older lineages at that. The Blacks, the Lestranges, the Selwyns, the Gaunts. Possibly others."

  "Not the Gaunts," Rowan said. "You'd have heard something."

  "No. Not the Gaunts." Ominis's voice was quiet. "But I can listen. My family may be estranged from me but they talk, and they talk loudly, and they assume a blind boy in the corner isn't paying attention."

  Sebastian had been watching this exchange with an expression Rowan couldn't read. He spoke now, and his voice had lost its competitive edge entirely. "This is about the people who tried to kill you."

  "Yes."

  "Then I'll help however I can." Sebastian met his eyes. "You taught me nonverbal casting when you didn't have to. You gave me the championship spot. Whatever you need, ask."

  Rowan nodded. He went up the stairs.

  Peeves found him on Thursday.

  Rowan was walking the fourth-floor corridor after dinner, heading back from the library with the ritual manual and two books on metamorphic theory he'd pulled from the stacks. His mind was on moonstone formation rates and whether ambient magical concentration could accelerate crystal growth by an order of magnitude or only a factor of two, which was the difference between finding usable moonstone on the ridge and spending the rest of the year hiking.

  Something cold and soft hit him in the back of the head.

  He spun around, wand up, and a rotten apple sailed past his ear and burst against the wall behind him. Another came from the opposite direction. He ducked and it splattered across the flagstones at his feet.

  A small, dark-eyed man in a bell-covered hat was floating upside down near the ceiling, cackling. He had a rotten pear in one hand and something brown and overripe in the other and was winding up for a throw.

  "Ickle student out all alone! Peevesy loves a target that doesn't duck!"

  The pear came fast. Rowan cast a Shield Charm and the fruit exploded against it, spraying pulp across the corridor. Peeves looked delighted.

  "Ooh, the ickle one can cast! How exciting! Let's see if the ickle one can cast and run!" He produced a handful of something from behind his back, which was impressive given that he'd been empty-handed a moment ago. Rotten plums, by the smell.

  "I'm not interested in playing," Rowan said. He picked up his books from where he'd dropped them.

  Peeves's face split into a grin that was too wide for a human face, which made sense because Peeves wasn't human. "Not interested in playing! Not interested in PLAYING! Peevesy lives to play! Playing is what Peevesy DOES!" He swooped lower, close enough that the bells on his hat jingled in Rowan's ear. "All work and no play makes the ickle student dull dull dull!"

  Rowan started walking. Peeves followed, hurling rotten fruit at irregular intervals, singing a song about a student who was too serious and eventually turned into a desk.

  "Playing is playing and working is working and never the two shall meet, unless you're Peevesy, who makes working into playing and playing into GRIEF!" He lobbed a plum at the back of Rowan's knees. Rowan sidestepped it without looking back.

  He was halfway to the staircase when it hit him.

  The thing that plays.

  He stopped in the middle of the corridor. The riddle from the Restricted Section journal, the one he'd copied into his own notebook over a year ago and hadn't been able to solve. The 1473 journal. The headmaster who'd spent forty years studying the vaults beneath the school.

  What has no door, yet bars the way? What holds treasure but refuses to give? What speaks without a voice and guards without hands?

  The answer is not the vault itself. The answer is the thing that plays.

  Peeves. A poltergeist. A spirit of chaos that played tricks, played games, played with everyone and everything it touched. The thing that plays.

  A rotten apple hit him in the shoulder. He barely felt it.

  "Peeves."

  "WHAT?" Peeves was right behind him, a bruised pear cocked back in one hand, his face lit up with the pure joy of someone who had found a target that wasn't running away fast enough.

  "The cursed vaults. Beneath the school."

  The change was instant.

  The pear in Peeves's hand disappeared. The grin vanished. The manic energy that animated every inch of him drained away and what was left was something Rowan had never seen in a poltergeist and didn't want to see again. Peeves was still. Completely, unnaturally still, hanging in the air like a puppet whose strings had gone taut. His eyes, which had been darting and gleeful a second ago, fixed on Rowan and didn't move.

  When he spoke, his voice was different. Lower and slower. The singsong cadence gone, replaced by something that sounded like it came from a long way away and a long time ago.

  "You found the journal."

  It wasn't a question. Rowan's skin prickled. The corridor felt colder.

  "Yes."

  Peeves drifted downward until he was at eye level. This close, Rowan could see that something was wrong with his face. The features were the same but the expression behind them was different, as though something older and more deliberate was looking out through Peeves's eyes. The bells on his hat didn't jingle. The air around him was still.

  "Students aren't supposed to find the journal. Old Rackham hid it well." Peeves tilted his head. The movement was too smooth, too controlled. "But someone always finds it eventually. That's what journals are for."

  He drifted closer. His eyes hadn't blinked.

  "I know what's in the vaults. I know what they do. I know what happens to the people who open them, and I know what happened to the last person who finished all five." His lips moved into something that wasn't a smile. "Four centuries ago. She walked in a student and walked out something else entirely. Something more." Peeves's voice dropped. "Each vault you complete gives you a piece of what she got."

  "What do I have to do?"

  "You already know where the first one is. You've been walking the fifth floor for years, pretending you don't feel it pulling at you." Peeves's voice dropped lower. "You can't fight it the way you fight everything else."

  "Then how do I fight it?"

  "You'll have to figure that out yourself." Peeves's mouth twitched. "But I'll enjoy watching you try everything you know and learn that none of it is enough." The wrongness behind his face flickered. "The vaults take something from everyone who enters them. Even the ones who win."

  Then the stillness broke. The bells jingled. Peeves's eyes went wide and manic and he shot up toward the ceiling cackling, rotten fruit materializing in both hands.

  "Ickle student stood still for too long! SITTING DUCK!" He threw both at once. An apple caught Rowan in the chest and a plum burst against the wall and Peeves rocketed down the corridor shrieking about ducks and students and the terrible tragedy of clean robes.

  Rowan stood in the corridor, books in his arms, pulp and juice dripping down his front, his heart hammering.

  He found Iris in the common room. She was curled in the window seat with a Transfiguration essay, her quill moving in the steady rhythm that meant she was almost finished. She looked up when he sat down across from her.

  "You've got something on your robes." She wrinkled her nose. "Is that fruit?"

  "Peeves."

  "Lovely." She went back to her essay. "Did you get the metamorphic theory books?"

  "Yes." He sat there for a moment. "Iris, I need to tell you something. I found out about the cursed—"

  The words stopped in his throat. His mouth kept moving but no sound came out, as though something had reached into his chest and closed a fist around his voice. He sat there with his jaw working and his lungs pushing air and nothing coming out, and the sensation was so alien and so specific that for a moment he thought he'd been hexed.

  Iris had put her quill down. "Rowan?"

  He tried again, differently. "Peeves told me about—"

  The same thing. A door slamming shut somewhere between his intention and his mouth. The words existed in his mind, fully formed, and they could not reach the air.

  "Are you all right? You look like you're choking on something."

  "I'm fine." Those words came out easily. He could talk about anything else. He could describe the weather, discuss the Transfiguration essay, tell her about the thornback clicking patterns. He just couldn't say the thing he'd come to say. "Actually, I wanted to ask about your mapping calculations for Saturday. The lunar alignment data you collected on the shelf."

  Iris looked at him for a long moment. She knew him well enough to know that wasn't what he'd sat down to say.

  "The alignment data is in my notes. I'll bring it Saturday." She picked up her quill. "When you're ready to tell me whatever that actually was, I'll be here."

  She went back to her essay. Rowan sat there and thought about it. Speaking hadn't worked. Maybe the block was only on his voice. He reached for Iris's mind with a light Legilimency probe, the gentlest touch he could manage, carrying the image of the vault door and the shape of what Peeves had told him.

  The probe connected and then collapsed. The information sheared away at the point of transfer, the images dissolving before they could form in the space between his mind and hers. Iris didn't even flinch. She hadn't felt anything. Whatever was stopping him operated at a level deeper than speech or writing or thought, and it didn't care which method he tried.

  Rowan went upstairs. He sat on his bed and pulled out his journal and tried writing it. The cursed vaults are— The ink vanished as it touched the page. The parchment was blank and dry, as though he'd never written anything at all.

  He stared at the empty page. Lawrence was asleep. Hector was reading his Quidditch magazine. Somewhere far below, in the pipes or the walls or the foundations of the castle itself, something hummed at a frequency just below hearing, and he wasn't sure if he was imagining it or if it had always been there and he was only now able to notice.

  He turned to the riddle page, the handwriting already looking younger than his current hand.

  The answer is the thing that plays.

  He closed the journal and put it under his pillow and lay in the dark and didn't sleep for a long time.