Myrnin's actual lab was a deserted wreck.

Whether it was Bishop's goons, vandals, or just Myrnin being crazy, there was even more destruction now than the last time Claire had seen the place. Virtually all the glass had been shattered; it covered the floor in a deadly glitter. Tables had been overturned and floor in a deadly glitter. Tables had been overturned and splintered. Books had been ripped to shreds, with the leather and cloth covers gutted and empty, tossed on piles of trash.

The whole place smelled foul with spilled chemicals and molding paper.

Myrnin said nothing as they descended the steps into the mess, but on the last step, he paused and sat down - more like fell down, actually. Claire wasn't sure what to do, so she waited.

"You okay?" she finally asked. He slowly shook his head.

"I've lived here a long time," Myrnin said. "Mostly by choice, as it happens; I've always preferred a lab to a palace, which Amelie never really understood, although she humored me. I know it's only a place, only things. I didn't expect to feel so much . . . loss." He was silent again for a moment, and then sighed. "I shall have to rebuild again. But it will be a bother."

"But . . . not right now, right?" Because the last thing Claire wanted to do was get a broom and a dump truck to pick up all that broken glass when the fate of Morganville was riding on their staying focused.

"Of course not." He leaped up and - to her shock - walked across the broken glass. In flip-flops. Not even pausing when the glass got ankle-deep. Claire looked down at her own shoes - high-top sneakers - and sighed. Then she very carefully followed him, shoving a path through the glass as she went while Myrnin heedlessly crunched his way through.

"You're hurting yourself!" she called.

"Good," he shot back. "Life is pain, child. Ah! Excellent." He crouched down, brushed a clear spot on the floor, and picked up something that looked like a mouse skeleton. He examined it curiously for a few seconds, then tossed it over his shoulder. Claire ducked as it sailed past. "They didn't find it."

"Find what?"

"The entrance," he said. "To the machine."

"What machine?"

Myrnin smiled his best, looniest smile at her, and punched his fist down into the bare floor, which buckled and groaned. He punched again, and again - and an entire six-foot section of the floor just collapsed into a big black hole. "I covered it over," he said. "Clever, yes? It used to be a trapdoor, but that seemed just a bit too easy."

Claire realized her mouth was gaping open. "We could have fallen right through that," she said.

"Don't be overly dramatic. I calculated your weight. You were perfectly safe, so long as you weren't carrying anything too heavy." Myrnin waved at her to join him, but before she got halfway there, he jumped down into the hole and disappeared.

"Perfect." She sighed. When she finally reached the edge, she peered down, but it was pitch-black . . . and then there was the sound of a scratch, and a flame came to life, glowing on Myrnin's face a dozen feet down. He lit an oil lamp and set it aside. "Where are the stairs?"

"There aren't any," he said. "Jump."

"I can't!"

"I'll catch you. Jump."

That was a level of trust she really never wanted to have with Myrnin, but . . . there was no sign of mania in him, and he watched her with steady concentration.

"If you don't catch me, I'm totally killing you. You know that, right?"

He raised a skeptical eyebrow, but didn't dispute that. "Jump!"

She did, squealing as she fell - and then she landed in his strong, cold arms, and at close range, his eyes were wide and dark and almost - almost - human.

"See?" he murmured. "Not so bad as all that, was it?"

"Yeah, it was great. You can put me down now."

"What? Oh. Yes." He let her slide to the ground, and picked up the oil lamp. "This way."

"Where are we?" Because it looked like wide, industrial tunnels, obviously pretty old. Original construction, probably.

"Catacombs," he said. "Or drainage tunnels? I forget how we originally planned it. Doesn't matter; it's all been sealed off for ages. Mind the dead man, my dear."

She looked down and saw that she was standing not on some random sticks, but on bones. Bones in a tattered, ancient shirt and trousers. And there was a white skull staring at her from nearby, too. Claire screamed and jumped aside. "What the hell, Myrnin?"

"Unwanted visitor," he said. "It happens. Oh, don't worry; I didn't kill him. I didn't have to - there are plenty of safeguards in place. Now come on, stop acting like you've never seen a dead man before. I told you, this is important."

"Who was he?"

"What does it matter? He's dust, child. And we are not, as yet, although at this rate we certainly may be before we get where we're going. Come on!"

She didn't want to, but she wanted to stay inside the circle of the lamplight. Dark places in Morganville really were full of things that could eat you. She joined Myrnin, breathless, as he marched down an endlessly long tunnel that seemed to appear ten feet ahead and disappear ten feet behind them.

And suddenly, the roof disappeared, and there was a cave. A big one.

"Hold this," Myrnin said, and passed her the lamp. She juggled it, careful to avoid hot glass and metal, and Myrnin opened a rusty cabinet on the wall of the tunnel and pulled down an enormous lever.

The lamp became completely redundant as bright lights began to shine, snapping on one by one in a circle around the huge cavern. The beams glittered off a tangled mass of glass and metal, and as Claire blinked, things came into focus.

"What is that?"

"My difference engine," Myrnin said. "The latest version, at least. I built the core of it three hundred years ago, but I've added to and embroidered on it over the years. Oh, I know what you're thinking - this isn't Bab bage's design, that limited and stupid thing. No, this is half art, half artifice. With a good dash of genius, if I might say so."

It looked like a huge pipe organ, with rows and rows of thin metal plates all moving and clacking together in vertical columns. The whole thing hissed with steam. In and around that were spaghetti tangles of cables, tubes, and - in some cases - colorful duct tape. There were three huge glass squares, too thick to be monitors, and in the middle was a giant keyboard with every key the size of Claire's entire hand. Only instead of letters on it, there were symbols. Some of them - many of them - she knew from her studies with Myrnin about alchemy. Some of them were vampire symbols. A few were just . . . blank, like maybe there'd been something on them once, but it had worn completely off.

Myrnin patted the dirty metal flank of the beast affectionately. It let out a hiss from several holes in the tubing. "This is Ada. She's what drives Morganville," Myrnin said. "And I want you to learn how to use her."

Claire stared at it, then at him, then at the machine once again. "You're kidding."

And the machine said, "No. He's not. Unfortunately."

Claire had seen a lot of weird stuff since moving to Morganville, but a living, steam-operated Frankenstein of a computer, built out of wood and scraps?

That was just too much.

She sat down suddenly on the hard rocks, gasping for breath, and rested her head on her trembling palms. Distantly, she heard the computer - that was what it was, right? - ask, "Did you break another one, Myrnin?" and Myrnin answered, "You are not to speak until spoken to, Ada. How many times do I have to tell you?"

Claire honestly didn't even know how to start to deal with this. She just sat, struggling to keep herself from freaking out totally, and Myrnin finally flopped down next to her. He reclined, with his arms folded behind his head, staring straight up.

"What do you want to know?" he asked.

"I don't," she said, and wiped trickles of tears from her face. "I don't want to know anything anymore. I think I'm going crazy."

"Well, it's always a possibility." He shrugged. "Ada is a living mind inside an artificial form. A brilliant woman - a former assistant of mine, actually. This preserved the best parts of her. I have never regretted taking the steps to integrate technology and humanity."

"Well, of course you wouldn't. I have," Ada said, from nowhere in particular. Claire shuddered. There was something not quite right about that voice, as if it was coming out of some old, cheap AM radio speakers that had been blown out a few times. "Tell your new friend the truth, Myrnin. It's the least you can do."

He closed his eyes. "Ada was dying because I had a lapse."

"In other words," the computer said acidly, "he killed me. And then he trapped me inside this box. Forever. The fact that he doesn't regret it only proves how far from human he is."

"You are not trapped in the box forever," Myrnin said, "as you well know. But I still need you, so you will simply have to stop your endless wailing and get on with things. If you want an escape, research your way out."

"Or you'll what?"

Myrnin's eyes snapped open, and he bared his fangs - not that he could bite the computer. It was just a reaction of frustration, Claire thought. "Or I'll disconnect your puzzle sets," he said, "and you can read the works of Bulwer-Lytton for entertainment for the next twenty years before I take pity on you."

Ada was notably silent in response to that, and Myrnin folded up his fangs and smiled. "Now," he said to Claire, "let me explain Ada. She is the life force that powers the town, of course; without her, we could not operate the portals, and we could not maintain the invisible fields that ensure Morganville residents stay put, and suffer memory loss if they manage to make their way out of town. The drawback is that Ada is a living being, and living beings have . . . moods. Feelings. She has been known to grow fond of people, and to sometimes interfere. Such as with your friend Michael."

"Michael?" Claire blinked, intrigued despite everything. She didn't want to know more. . . . Oh, hell, yes she did. She really did. "What do you mean?"

"I mean that Ada interceded to keep Michael alive, because she could. Ada's presence is most felt in the Founder Houses, which are closely linked to her; she can, with enough of an effort, manifest in them, or anywhere there is a portal, for short periods of time. In Michael's case, she chose to save his life by storing him in the matrix of the Glass House rather than allowing him to die when Oliver attempted, and failed, to turn him into a vampire."

"She didn't just save him, she saved him," Claire said. "Like a computer saving a crashed file."

"I suppose, if you want to put it in mundane terms." Myrnin yawned. "I told her to let him go. She ignored me. She does that."

"Frequently," Ada's disembodied voice said. "And with great satisfaction. So. You are the girl from the Glass House. Myrnin's new pet."

"I . . ." Claire wasn't sure how to respond to that, so she settled for a quick shrug. "I guess."

"You've done well," Ada said. "You work the portals without much understanding of how they function or how to create them, but I suppose that most modern children couldn't begin to construct the toys with which they play."

Claire's cell phone suddenly rang, its cheerful electronic tone startling in the silence. She jumped, flailed, and fished it out of her pocket, only to have it immediately go dark.

"Did you do that?" she asked.

"Do what?" Ada asked, but there was a dark, amused edge to the words. "Oh, do forgive. I've got little enough to occupy me down here in the dungeon. In my box."

"Ada." Myrnin sighed. "I brought her here so you could explain to her how to maintain your functions, not to have her listen to your endlessly inventive complaints."

Ada said nothing. Nothing at all. In the silence, Claire heard the steady whir and click of gears turning, and the hiss of steam - but Ada stayed quiet.

"She's pouting," Myrnin said, and heaved himself up to a sitting position. "Don't worry, my dear. You can trust Claire. Here, let me introduce you properly."

Myrnin's idea of a proper introduction was to grab Claire by the arm and haul her over in front of the machine. Before she could yell at him to let go, he slipped back a metal cover and pushed her hand down on a metal plate . . . and something pierced her palm, lightning fast, like a snakebite. Claire tried to snatch her hand back, but something - some force - held it in place.

She could feel blood trickling out of the hot, aching wound. "Let go!" she yelled, and kicked the machine in fury. "Hey! Hey!"

Ada giggled. It was a weirdly metallic sound; up close, she really didn't sound human at all, more like parts grinding together inside.

The force holding Claire's hand in place suddenly let go, and she stumbled back, clutching her burning hand to her chest and trying - without much success - to stop herself from gasping for breath. She was afraid to look, but she forced herself to open her left hand.

There was a small puncture wound in the middle of her palm, a red circle about the size of a pencil point; there was a whiter circle all around it, like a target. As Claire watched, the white faded.

Blood trickled out of the hole in her skin in fat red drops. Claire looked at Myrnin, who was standing a few feet away; he was gazing at her hand with fascination.

Ewwwwww.

Claire made a fist, willing the bleeding to stop. "What the hell was that?"

"That?" Myrnin didn't seem to be able to take his gaze off of her fist. "Oh, it's simple enough. Ada needed to know who you were. She'll know you now, and she'll follow your orders."

Ada made a sound suspiciously like a strangled cough.

"That doesn't explain why she bit me!" Claire said.

Myrnin blinked. "Blood is the fuel that drives the engine, my dear. As with us all. Ada requires regular infusions of blood to operate."

"You never heard of plugging her in? My God, Myrnin, you made a vampire computer?"

"I . . ." He seemed honestly unsure how to answer that, and finally gave up. "She requires about a pint of blood each month - not refrigerated blood; it should be warmed to at least room temperature, preferably to body temperature, of course. I generally feed her close to the beginning of the month, though she can, in a pinch, go weeks without nourishment. Oh, and do feed her at night. Blood is less effective when offered under the influence of the sun. We do work according to hermetic rules here, you know."

"You're insane," Claire said. She backed up against a wall and stood there staring at him. "Seriously. Insane."

He didn't pay any attention to her at all. "You also need to recalibrate her once on each solstice day, winter and summer, to accommodate the shifting influences of sun and moon. You do remember the hermetic symbology I taught you, don't you? Well, the formula is quite simple. I've noted it down for you, here." Myrnin patted his jacket pockets, and finally came up with a much-scratched-out, torn scrap of grimy paper, which he offered to Claire.

She didn't take it. "This is crazy," she said again, as if it was really important that he understand it. Myrnin slowly raised his eyebrows. "You built a vampire computer. Out of wood. And glass. You're not . . . This isn't . . ."

He patted her gently on the shoulder. "This is Morganville, dear Claire. You should know by now that it would not be what you expect." With a sudden burst of energy, Myrnin took Claire's unwilling hand, slapped the paper into it, and bounced to his feet. "Ada!"

"What?" The computer sounded surly. Hurt. She's not even real, Claire told herself. Yeah. She's not real, and she drinks blood. She just drank mine.

"You will accept all commands from Claire Danvers as my own. Do you understand me?"

"All too clearly." Ada sighed. "Very well. I shall record her essence for future reference."

Myrnin turned back to Claire and folded her hand over the scrap of paper. His fingernails were filthy and sharp, and she shuddered at how cold his touch was. "Please," he said. "You must keep this safe. It's the only record of the sequence. I made it to remind myself, in case . . . when I forgot. If you get the sequence wrong, you could risk killing her. Or worse."

Claire shuddered. "What could be worse than her being here at all?"

"Turning her against us," Myrnin said. "And believe me, dear, you wouldn't want that to happen."