Barry still had some misgivings about taking Agatha to meet the Castle properly, but there wasn't much to be done about it. He pushed the feeling aside to grin at the outflier pilot, who by this point was probably starting to feel like he'd been assigned to Heterodyne-ferrying duty, as they docked. He clanked his way through Castle Wulfenbach, which was beginning to look much more densely constructed. The guards let him into the completed section, where he found Klaus's door open and his friend himself scowling at paperwork. Barry cleared his throat. "Not that there's any particular rush," he said lightly, "but I think I do have an appointment."

Klaus put the paperwork aside, looking somewhat relieved at the excuse. "We wouldn't want Castle Heterodyne to get impatient," he said.

"It has been giggling at me," Barry said. "And I've barely been inside. It also thinks I should give you an oubliette as a housewarming present, by the way."

"On an airship?" said Klaus.

"Well, a bottomless pit would be superfluous."

"This is true. If your house wants to give me presents I'd rather have a spare torchman," said Klaus. He stood up and walked over to the door. "Time to get going?"

"Yes. Ah -" They'd both been busy. Barry wasn't sure exactly what the school procedure would have been. "Agatha asked me if she could bring a friend. Have you had a permission request or anything?"

"Yes." Klaus looked worried, but resigned. "From Gil. I told him he could come."

"I thought she'd ask him. I already told it not to tell him, well..." Barry trailed off. "I don't think I can talk it into holding off on the Doom Bell, though."

"I'll give orders to get out of range before we leave," said Klaus. "There should be time."

"I would think so." Gil, of course, would still be with them. Well, all the children in Mechanicsburg coped, and the Castle probably wouldn't let him get seriously hurt even if he somehow fell off anything. "Let's go, then." He went over to rap at the school's entrance.

Von Pinn opened it so quickly Barry wondered if she'd been waiting just inside. "Herr Baron. Master Heterodyne. The children are-" She effortlessly reached down and blocked Agatha's attempt to dash past her. "Ready."

Barry's mouth twitched, and he held out a hand. Von Pinn allowed Agatha to walk past a bit more sedately to hug him. "So I see." He nodded to Gil. "Good to see you again, too."

Gil smiled up at him. "Thank you."

"We don't take a lot of visitors to Castle Heterodyne," Barry said seriously. "You'll, ah, probably see why. But you're Agatha's friend and I've told it to protect you like you were part of the family." He glanced at Klaus. "I grew up there. It may be more helpful to you if Klaus tries to give you an idea what to expect."

"I expect Agatha's told you the Castle is alive," said Klaus. "Within itself it can do almost anything, but it won't actually do most of what it will threaten you with. It has a nasty sense of humour, but it does obey Barry." He hesitated and then put a hand on Gil's shoulder. "I wouldn't take any of my students there if I believed they would come to harm. Just be careful, it contains a lot of things that shouldn't be meddled with even when it's not trying to hurt you with them. And, after Agatha is accepted, it will ring the Doom Bell. It brings up bad memories for anyone who hears it, but it will be over quite soon. And it's best to get used to such things, everyone in Mechanicsburg does."

Gil looked up at him wide eyed and nodded solemnly. "I'll be careful," he said. He glanced at Agatha to see if she was listening as well.

Agatha was looking up thoughtfully at the Baron, then regarded Barry with one of those expressions that made him wonder if she was supposed to be quite like that when she wasn't even five yet. "Will it listen to me too?" She considered for a moment. "After it bites me?"

Barry reflected that Gil must have received an interesting idea of the Castle already. "Sometimes," he said. "After you grow up, it will listen to you more than me."

"Do you want it to listen to you?" asked Gil. He thought about that for a moment. "It would definitely be better than it not listening to you, but..."

"If I have to tell it not to hurt my friends," Agatha said, "it had better."

Barry found himself suddenly much less worried. "One of our ancestors modelled it on his own personality," he began.

Agatha gave him a skeptical look. "He bit people?"

"I doubt it," said Klaus. "Although there are rumours of a Heterodyne Vampire."

"Oh, we won't run into him," Barry said, all apparent innocence. "I wasn't planning to go to the crypt."

Gil gave Agatha a rather wide eyed look, not quite sure whether to believe what the adults were saying.

"Come on," said Klaus. "If we don't get going the Castle will be sending torchmen up to fetch us."

"It could get a little impatient," Barry conceded, and they set off. He resisted picking Agatha up for now - it was, after all, demonstrable that she wasn't going to vanish if they got too far out of contact, and it was a short walk.

She was giving him a skeptical look every time he glanced down at her. As they reached the outflier and he took his seat, she rested her clasped hands on his knee. "Uncle Barry," she said, with a severity she had to be imitating from Von Pinn, "is there a real vampire? I thought they were strictly folkloric."

Barry shot Klaus a look, mostly to give himself time to control the urge to laugh at her tone. "People do a lot of strange things," he said, when he could trust himself to speak, "to themselves and each other. There was a Heterodyne whose revival went wrong and he got a taste for blood, but he's all the way dead by now." His son was a bit more complicated, but he wasn't going to get into that. He lifted Agatha into her own seat, instead.

Gil, from his place next to Agatha, leant over and whispered, "You might have been right about your family."

Barry regarded Gil with some amusement. "What did she say?"

Gil looked faintly embarrassed, but Agatha said plainly, "I said they sound weird," sitting back to watch the pilot.

Barry shrugged. "Really can't argue with that."

Castle Heterodyne made a minor show to welcome them, of course, flinging the doors open with a boom. (Closing doors with a boom was one thing. Opening them that way was just showing off. Barry considered annoying it by suggesting it needed its hinge coordination recalibrated, but decided this was not the time to be unnecessarily antagonistic.) Agatha clung firmly to his hand and Gil's, although Barry wasn't quite sure whether the latter was for her own comfort or a protective impulse. "Hello, Castle," she piped up.

"Greetings, Lady Heterodyne, if my lady you be," the Castle boomed. "I have prepared a way to the chapel."

Agatha blinked and looked up at Barry. "Wasn't there one before?" she asked.

"It may mean it decorated," Barry murmured. And wasn't that a worrying thought. "But it does rearrange the floor plan sometimes. Hello to you too," he added blandly, in the direction of the doorway ahead of them.

It had decorated. Rather more tastefully than he was expecting, with looping curlicues and trilobites and only the occasional grinning skull. It had also made sure it was obvious that the elegant walkway over the courtyard was by no imaginable measure structurally sound. Agatha's hand slithered out of his, and he looked over to find her and Gil crouched down to peer underneath the edge.

Barry cleared his throat. Agatha ran back over hastily and joined him to cross the bridge. The stones held, under all four of them. A winding stair, with - voices ahead? That didn't sound like the Castle's voice...

Barry stopped and rubbed his eyes as the chapel door came into view.

There was a Muse sitting outside it. Ragged hair, her gown now only a few rags, but the intricate sleek structure, the fleur-de-lis markings, were impossible to mistake. Chains had been welded to her ankles and wrists, but were broken off short now. The great wings, most of their fabric feathers gone, arched with an odd air of irritation. Well, maybe not that odd, all things considered. "...Otilia?"

"No," said the Muse, with some annoyance. "I am Castle Heterodyne."

"Part of Castle Heterodyne," corrected the Castle, its voice coming from inside the chapel.

Barry looked at Klaus, then down at the children. "This is evidently going to be more complex than I was expecting." Why was a Muse claiming to be Castle Heterodyne? Although, if he could listen past the voice, he supposed the tone was very Castle-like. "Castle," he said, "please, explain." A very brief pause, then to the Muse, "You start."

The Muse stood up. "Lucrezia. She has a laboratory beneath me, where I could not find it, and she downloaded a copy of my personality there, transferring me into this body. The Muse she transferred elsewhere."

Barry exhaled slowly between his teeth. Mind transfers, again. Not a good sign. "Where did she put the-" A possible answer occurred to him. Harmonised with the facts, like a struck chord. Lucrezia's creation. Lucrezia's creation who loathed her and didn't say why, who lost her mind when she couldn't protect her charge. "Von Pinn?"

"Yes." The Muse looked at him, wings flaring behind it. "You must return her to this body."

"She didn't come with us," said Barry. "I'll talk to her when we get back to Castle Wulfenbach."

"Talking won't help. You need to bring her here."

Barry paused. "Excuse me?"

"If she could have told you she would have done so," interrupted the voice from the chapel.

"...Lucrezia would have built compulsions into the new body. Of course." Barry rubbed a hand over his face. The idea of yanking somebody's mind into a different body based on the Castle's word alone worried him, but the whole thing rang of truth. The Muse - or the Muse body - was there. It was bizarrely easy to imagine Von Pinn as the Muse of Protection. And it was uncomfortably possible that she was rendered not only incapable of saying what had happened, but incapable of agreeing to the reversal. He hoped not. "You know where the lab is now, I assume. I'll need to see her equipment. The only mind-transfer devices I'm familiar with are strictly biological."

"There is a secret passage behind her -" the Muse began, only for the chapel to interrupt it.

"There isn't. I know all the passages inside my walls."

The Muse's wings flared. "I walked up it." It glared at the chapel and turned to Barry. "Please reunite me with this Castle, I clearly have the better part of our intellect."

Don't laugh at the Castle, Barry instructed himself. He cleared his throat. "Well, I'll certainly have to do something. No matter how intricate Van Rijn's work is, I can't imagine there's room for two of you in there."

"I suppose I survived it once," grumbled the Castle from the chapel.

"You'll be fine," Barry told it, then glanced back at the Muse. "I don't know if it's explained about the earlier reintegration problems."

"Somewhat," said the Muse.

The Castle sighed. "I don't actually wish to lose the memories of that part of myself."

"It might be easier this time," Barry offered. "Two of you instead of a dozen, and both relatively calm. However-" He looked down at Agatha and discovered she was trying to peer between the chapel doors. "Perhaps we can get the recognition taken care of first."

"That might be best," agreed the Muse. It stepped aside and bowed, just as the chapel doors swung inwards.

Agatha stumbled a little, and Barry rested a hand on her shoulder and tried not to sigh at all the skulls. "Welcome to the family chapel of the Heterodynes," he said, a little resignedly. "Agatha, ah... watch your step." He really wanted to step between the skulls himself - even if they'd been trying to steal his house, walking on what was left of them was uncomfortable.

The face folded up from the floor, focussing on Agatha. Gil stepped closer to her, grabbing her hand, and for a moment seemed to get its attention. "There's no need to protect her from me, so long as she is who she claims, little one. And if she is not there will be no point in trying." It returned its gaze to Agatha. "I congratulate you on having gained loyalty so young. He may be a fine consort one day."

"A what?" Agatha asked, sounding startled.

Barry wasn't sure whether to be exasperated at the Castle for bringing it up at all or relieved because this was, actually, its version of nice. Kind of. "The Castle thinks your father waited awfully late to get married," he said drily. "It's still not something you need to worry about any time soon."

"Okay." Agatha glanced up at Barry, looking a little worried; she squeezed Gil's hand, then let it go and walked forward, carefully picking her way among the skulls. "Uncle Barry says you're gonna bite me."

"Indeed I am," said the Castle. "But you are young and I will be, heh, gentle."

"You had better," Barry said under his breath, as he started to follow her. The Castle would hear him. It probably wouldn't care, but it would hear him.

Agatha looked back up at him, nose wrinkling, and for a second he thought she'd overheard, but that wasn't likely over the clattering of the disturbed skulls. "It sounds like one of the older kids when they're about to do something they only think is funny."

Barry shrugged a bit helplessly. "It does that a lot. But I was less than a day old and it didn't do much damage."

Agatha grimaced. She reached the face and stuck her arm between the giant teeth, as far as it would go. Barry felt her other hand tighten on his fingers, and he squeezed back as much as he dared.

Then she yelped, yanked her hand back, and promptly stuck it in her own mouth. Barry crouched down to tug at her arm. "Let me see." The hand he tugged free of her mouth was a little slimy by then, of course, but the cut to the web of the thumb was barely a scratch. "Ah, that's not so bad." He glanced up at the face. "You did get enough blood, didn't you?"

"Enough, yes. She is indeed your brother's child, and our Heterodyne." The Castle didn't bother to sound too dramatic on an announcement of something they'd all known anyway.

"There we go, then." Barry hesitated. "And thank you for taking it easy on her." He raked a hand back through his hair and regarded the Muse. "I can go ahead and hook you two together fairly quickly, I think, either before or after we announce Agatha. After that-" He turned to Klaus. "I'm not sure we'd be able to get Von Pinn to come here if we left Agatha on Castle Wulfenbach." Or Gil, for that matter, but he was trying to be circumspect.

"Is there such a thing as a safe place to leave them inside the Castle?" Klaus asked. "I'd rather keep them close."

"Gradok Heterodyne's childhood laboratory was mostly used as a storeroom once he grew out of it," the Castle suggested. "It still contains a lot of his earlier inventions, and some tools, but nothing instantly deadly. Some of the tools are sharp, but I can take them away if they're being used that badly." Its tone suggested it didn't think much of any Heterodyne, however young, who would use basic equipment badly enough to seriously injure themselves. But that was all right, Agatha and Gil were both demonstrably capable of safely handling sharp objects. More so than some adult Sparks, really. Watching some people try to hold a scalpel was hair-raising.

"The 'Good' Heterodyne," said Klaus to Barry, dubiously.

"This would be from about a decade before the Cathedral," Barry told him. "It's probably fine. And... almost age-appropriate, anyway. He broke through when he was ten."

"Your family break through young," Klaus remarked, with a glance at Agatha. Possibly he was thinking about having the chance to observe her breakthrough, or possibly he was imagining the chaos it was likely to cause for his school. "If it doesn't contain anything worse than tools, it's probably safer than leaving them anywhere they'd get bored and wander off. And I'd really prefer not to resort to the cages."

"Some of us do. This way-" Barry glanced down at the children, who looked like they weren't quite sure if the cages were a joke or not, and then glanced back up at Klaus and grinned as they set off. "It may be full of dragons. Gradok made Franz."

"I'm not sure if that's reassuring or not," said Klaus. "I like Franz, but he does consider people to be edible."

"True, but without much enthusiasm." Sometimes that was as good as it got. "I suppose that must have been a later development," Barry added reflectively. "According to the notebooks, he started out as a particularly dragony piggy bank."

"Really?" asked Gil. "How big is he now?"

"You're about the size of one of his fingers," Barry told him. "Gradok made him to guard all his treasure, and get bigger as needed. Only, Gradok was still a kid at the time and had two older siblings, so he wasn't ever expecting to be the Heterodyne himself..." He tried not to sigh. Okay. Occasionally he could sympathise with some of his ancestors. He could also remember learning Klaus had lost both his own brothers and finding it unimaginable.

"It must be very hard to steal from your family, if all your money is in a dragon," said Gil. "Do you have to take it out of him to pay for things?"

Barry shook off the melancholy moment. "We keep some out so we don't have to wake him up all the time. He sleeps a lot." His mouth quirked. "When Bill and I were really little, our father would occasionally rouse him when the town was under attack, and put us inside the vault."

Gil thought about that, brows drawing together solemnly. "Were you scared?"

"I... think I was too young to realize there was anything to be scared of. I don't remember it very well. Mostly an impression of being put inside, and Franz being grouchy because he was still half asleep." Bill and a blue lamp, and gold coins sliding around. Blinking in the daylight when their mother pulled them out. "Considering some of the things Father considered fun and educational, I guess those must have been some of the more worrying attacks."

Gil nodded, still frowning.

"What did he think was fun and educational?" Agatha asked. "Besides being inside a dragon?"

"Ah..." Barry rubbed his forehead, trying to think of examples that would get the idea across without the descriptions themselves being too awful. "He did have us watch some attacks on the town later. Vivisections." He shot Klaus a rueful look. "I understand he made Bill set the Wulfenbachs' great hall on fire once."

"I remember that," said Klaus. "In retrospect I think Bill only did it so he could aim at the parts that would be easiest to put out."

"He was afraid if Father took back the flamethrower, he'd aim at people," Barry agreed ruefully.

"But why would he want to do that?" Agatha asked, distressed.

Barry sighed and scooped her up to hug her. "He didn't tend to think about being nice to anybody who wasn't from Mechanicsburg. Mother spent a lot of time explaining why we should."

The Castle made a disapproving grinding sound. Klaus gave the nearest wall a wry look. "The Castle still doesn't agree, but fortunately it can't leave Mechanicsburg," he said. "And it makes an exception for friends of Heterodynes, even while grumbling about friends not being worth bothering with," he added to Gil, who glanced at Agatha and looked reassured.

Barry's mouth quirked. "Good summary." Agatha squirmed, so he let her down, whereupon she promptly and firmly latched onto Gil's hand again. "And - here we are." Gradok's laboratory had a long, slender dragon sculpted around the door, regarding the doorknob with evident suspicion. Barry turned it anyway, revealing a room with low workbenches, stepstools, a conglomeration of boxes toward the back, and unboxed clanks and tools laid out in what had probably been neat rows before the damage and repair of the Castle. The sun coming through the window highlighted a hazy layer of dust, but that was the only sign of neglect.

Klaus walked in and gave the clanks out on the benches a swift glance before nodding. "This looks safe enough," he said, then paused to open up a dragon's claws. "Fascinating. Very elegant for a Spark just past breakthrough, especially one so young."

Agatha moved in as well, looking around in evident delight and towing Gil with her - not that he needed much towing.

"The 'good' designation aside," Barry said, picking up a small and equally dragony bellows, "Gradok was a very impressive Spark. Attentive to detail." He checked to make sure it was only a bellows rather than producing its own fire, then used it to puff clean a section of workbench. "I'm not sure what he'd have done, if he hadn't spent most of his life trying to figure out what happened to his sister."

The look Klaus gave him at that was sympathetic but he didn't say anything, just turned to the children. "Will you two be all right here while we sort the Castle out? There will be a moment when it shuts down briefly, so if the lights go out it's nothing to worry about."

"I think we'll be fine," Agatha said. By this point she had climbed up onto a short stack of boxes to peer into a higher one and was almost at eye level with Barry, thoroughly smudged with dust already and starry-eyed when she turned to face them. "This place looks like fun."

Gil nodded enthusiastically, already pulling a stool over to climb up and peer into a box of his own.

"Okay, good." This should definitely keep them busy. Barry paused on his way out. "Tell the Castle if you get hungry and it can pass a message to the cooks." He wasn't sure Agatha was listening, but Gil looked up and nodded. Barry could hear them start to chatter as the door closed, and he looked up to nod at the towering Muse. "All right," he said, "library."