Something cold touched the back of Knuckles' neck and he ducked instinctively, spun round, swung for whatever unseen attacker had managed to get so close. He stopped abruptly at the realisation that it was only something dripping from above and that, furthermore, Sonic was laughing at him.

"Jumpy much?"

Knuckles glared at him and Sonic subsided. "Don't worry, Knux, I've been here before. No problem."

Sonic lifted one foot in preparation to speed off without waiting for an answer but instead squealed loudly and ducked himself as he also got dripped on. This time both Tails and Knuckles laughed as he shook out his fur and spines. It looked so undignified it was impossible not to.

Tails looked up curiously. "I don't think it's anything poisonous. It doesn't sting does it?"

Knuckles shook his head.

"Oh great, that's a comfort," Sonic griped. "Can we just get going?

Knuckles looked at him, wondering how he'd already decided a direction with no clues in sight.

"Go where?"

Sonic shrugged. "Dunno. Wherever. Somewhere with some answers."

Knuckles frowned. The hedgehog clearly had no idea at all in spite of his enthusiasm to move on. He tapped his foot then spoke again.

"Unless you think that an explanation will just appear into thin air right here?"

Knuckles didn't of course but couldn't help looking around anyway. It was evening but he hadn't noticed it because of all the artificial light. Huge buildings surrounded them, tower blocks and industrial sites and pylons criss-crossing and climbing to the sky. It was between two of these that the leaky pipe which had dripped on them stretched. The air was damp and cold in spite of the steam that rose from some of the machinery around them, and it stank.

A shudder which had nothing to do with the drips or the temperature, ran down Knuckles' spine.

"No," he said, making sure none of of the tremor reached his voice. "Let's not stay here."

He moved off but had only gone two paces when Sonic was ahead of him again and grinning.

"You know what the fastest way through here is?"

Almost grateful for an excuse to be annoyed instead of unnervingly anxious, Knuckles shot back at once.

"And how would I know that, hedgehog?"

Sonic ignored the irritation in his voice completely.

"Hedgehog is right. Hedgehog is absolutely the fastest way through here. And hedgehog halfpipe too, not plodding on pavements. Want me to show you?"

Tails grinned. "I do. I remember!"

Knuckles did not like the look of active anticipation in either pair of eyes looking at him.

"Explain."

Sonic grin only widened at the demand.

"The pipes are a shortcut. They're awesome-steep. Super-fast. I can give you a tow..."

Tails had already taken hold of Sonic's proffered arm, their hands interlocked around each other's wrists in a way which looked practised. Knuckles eyed the pipes. They were wide enough to run on, even three abreast. For a moment the desire to be out of here as quickly as possible weighed against his dislike of putting himself literally into the hedgehog's hands.

He sighed and stretched out his own hand.

"If you take my arm off, I will take your head off with the other one."

Sonic only grinned wider and adjusted his grip.

"I won't. We got this. Run!"

Knuckles had to admit that the acceleration was within the bounds of sanity, far less than he'd seen Sonic deploy. It was just that it didn't stop. They were going faster and faster and his feet were only touching the ground every second or third step and the slipstream tugged at his quills, threatening to either yank his head back or pull him right off the ground. He ducked into it instead, shooting a glance across at Tails.

The fox was wasn't even trying to run. Instead he was propelling himself along as though flying at ground level, his toes just barely skimming the ground. He appeared entirely comfortable. Knuckles looked back in the direction they were running just in time as the pipe plunged downwards. He fought the urge to struggle free as he stomach dropped away with it, left at the top perhaps. He gritted his teeth and altered the angle of his quills thinking perhaps Tails was onto something. He felt the change instantly, his whole body pitching forward, his feet only touching the ground as intermittent course correction to stay in position with Sonic.

The hedgehog glanced round, pleased surprise on his face.

"That works! Whatever you're doing, do that."

And he accelerated again.

They hurtled round a loop and Knuckles lost contact with the pipe entirely.

Tails whooped, and adrenaline snatched a yell from Knuckles which was only half alarm.

Sonic laughed.

"Yeah! We got this!"

It crossed Knuckles' mind to ask where Sonic thought he was going, however fast it was he was likely to arrive there, but the speed whipped the words from his mouth unsaid. In any case, part of the question was answered as the pipe dived down again. It levelled out so abruptly that Knuckles stumbled, only sheer momentum and the constant tug onwards letting him get his feet back under him. They hurtled through an opening that barely cleared their heads and they were inside, heat hitting them like a wall.

Knuckles was reluctant to look around, afraid that moving his head too much would upset the fragile equilibrium he was managing to maintain on this harebrained ride that he'd somehow got himself involved in. Distantly though he was aware of the clutter of pipes, the heat, the even worse smell, and the noise. Machinery flashed by on either side, pools and vats of steaming goo glittered evilly in the corner of his vision. He had to fight the temptation to close his eyes. There was no way this kind of speed could be safe in here.

Sonic had apparently come to the same conclusion and the deceleration was shockingly fast. Knuckles barely stayed upright, boots offering little purchase on the slick metal. He flung out his arms and flared his spines and somehow stayed upright, though muscles protested up and down his legs and spine.

Sonic had also skidded to a halt, though he'd seemed more prepared and had twisted into it, flinging out his arms to finish with a flourish and facing back the way they'd come. Tails had ended up on his backside but was laughing, clearly unhurt.

Sonic looked around. "Well the decorating hasn't improved."

"This was the plan?" Knuckles asked incredulously. "Come in here? Into this..."

He failed to find an adequate word. He followed Sonic's gaze, looking around. The place was deeply oppressive and he couldn't begin to understand how the hedgehog was still smiling. For himself, Knuckles felt as though the sheer weight of metal around them was pressing in on him. No daylight, no starlight, not even any bare earth to let you know the rest of the world existed. Not a single, non-artificial thing in sight apart from them.

Sonic stopped smiling.

"Woah. Knuckles? You're looking a bit pale round the quills there, y'know?. Motion sick? Sorry about that." In spite of his words, he'd reached for Knuckles' arm again. Surely he didn't intend to carry on running did he? Knuckles stepped out of reach.

"I'm not ill."

Sonic stared at him a moment then shrugged. "Okay. If you say so. And yeah, this was the plan. We know Eggman's involved. The twirly-whatever-thing lands us right on his doorstep. Obviously the thing to do is ring the doorbell, right?"

Knuckles looked up at the dizzying towers of pipes. Sweat dampened his fur and his breathing had taken longer to slow down from running that it should have. He hoped he'd told Sonic the truth.

"This is Eggman's?" he asked, trying to pull some focus back together.

"Yep." Sonic said. "Grim huh?"

"It's horrible."

"Yeah, and that. It's one of the places I never managed to quite get rid of him from. But that means if there's some secret he's keeping, there's a chance he's keeping it here." Sonic smiled again. "So, y'know, always an upside!"

"It smells though," Tails put in. "Really really smells."

Sonic dropped a hand on Tails' shoulder and squeezed. "Yep. Still stinks."

The fox leaned into Sonic and smiled. "Bet if there's something in Eggman's computers about what's going on I can find it though."

"I bet you can too. Onwards?" Sonic waved at the route ahead where the reasons for their stop was obvious. This was an area for caution over speed. A place designed for robots and automation, not people. Heavy machinery cycled around and up and down in a shifting pattern that would crush any living thing that mis-stepped here. Knuckles tracked it with his eyes, warily, attentively, seeking a pattern that would allow a safe traversal. He was surprised, although he possibly shouldn't have been, to find the hedgehog doing the same.

After a moment Sonic pointed.

"There, there, theeeennnn there," he said, in rhythm with the shifting system.

Knuckles nodded, still watching the movements. "I agree."

Sonic gave a gasp of shock that made Knuckles turn in alarm to see what had happened, only to find the hedgehog laughing.

"You agree? With a hedgehog plan?"

"Shut up, Sonic," Knuckles said turning back to the route ahead. "Are we doing this or not?"

"We are. Tails? You see it?"

"Yup. No problem."

They stepped forward within a pace of each other but were only a few steps on before the screech of metal and the slam of a closing barrier behind them made them turn again.

"Uh oh," said Sonic, and for the first time Knuckles thought he sounded like he genuinely understood this place was dangerous. He was also staring down through the metal grating as though expecting it to catch fire beneath him. Knuckles looked down just as Sonic looked up and the hedgehog's eyes were as wide as Knuckles as ever seen them.

"Move!" he said. "Move movemove. Up. Go. Move!"

Knuckles was about to ask what the problem was but a gurgling, rushing sound answered him before he could open his mouth. Not fire then. Rather the opposite. Or given the vile, chemical reek of this place, something worse.

He eyed their route, picked his moment and jumped. Paused. Jumped again.

Sonic leapt past him, barely reaching the next safe landing spot as a shifting, twisting construction swung inexorably past them. Tails shot through the gap, catching Sonic's wrist and dragging him higher. Sonic dropped onto another sliding metal block and Knuckles paused, below him, waiting for the right alignment of the machinery to dodge up and past it.

"Faster faster faster!" Sonic shouted, all but hopping on the spot and staring at the blocked way ahead while he waited for the next window of opportunity.

"We can't go any faster, Sonic," Knuckles snapped. He glanced down to monitor the progress of the rising liquid beneath them. Was it toxic? If it was then they had a choice between getting crushed or poisoned because it was going to outpace them and soon.

Sonic had seen his opportunity and leapt neatly through the next gap, grabbing Tails as he went and getting hauled up further in return.

"Move, Knuckles!"

Knuckles ignored the urging, despite the temptation and waited for the right moment, but the lurid liquid had rushed up past him in the meantime and his jump was shortened abruptly as he was submerged. He fought down what would have been a startled gasp and lashed out for the rising block, intending to get a grip on it with his claws. Instead they slipped away, too little momentum and too strong and slick a surface. He fell back, paddling his legs to keep from sinking too far and landed back on the twisting machinery he'd just jumped from.

Somewhere up above him a splashing noise indicated the liquid had reached Sonic and Tails but whether they were all right or not would have to wait. Knuckles propelled himself off the machinery again, half jumping, half swimming and reached the next safe spot and the next.

He needed to breathe but this block was rising and the liquid no longer as dark, light from above filtered through and he jumped for the clear air above and found Sonic's and Tails' hands hauling him up and over the edge of the shaft.

He shot to his feet and looked back. The pink-tinged liquid was no longer rising, though another vat of it lay directly ahead. Sonic was panting and Tails wide-eyed and all three of them stood there for several seconds before anyone moved or spoke.

"Now we all stink." Sonic's voice shivered in spite of the muggy heat coming off the machinery and Tails also leaned into him as though for warmth.

Knuckles watched the two of them a moment, unsure of either the route or whether he should respond to the remark itself, or the near disaster.

"We do," he agreed after a moment and walked across to the edge of the reeking pool, assessing the distance across. Floating robotic devices moved back and forth across the surface, sampling or treating or collecting the stuff. He wondered if they'd hold their weight if the jump was too far.

It was the only way forward and after a moment Sonic joined him at the edge. Knuckles looked round and Sonic pulled a disgusted face.

"Tails, can you get us over?"

Tails took off at once.

"Sure."

"Take Sonic over," Knuckles said. "I can make it."

Sonic shrugged and Tails grabbed him as instructed. Knuckles took a running jump and angled his spines to a glide to lengthen it. He landed neatly beside them and Sonic grinned and moved off again without comment.

As they moved further into the plant the number of defensive bots increased and it became obvious that everyone was starting to tire. When Sonic jumped a split second too late at one of the flying caterpillar-style bots and was only saved from a nasty electrical shock by Knuckles grabbing his ankle mid-leap and dragging him back, they called a halt.

Sonic led them into a storage area of some kind. There were crates and barrels everywhere but they were empty and no bots patrolled it.

"We should keep going. I'm not tired," said Tails, though the fact he stumbled over the rim of the airlock-style door put the lie to his words.

"Uh huh," said Sonic. "Me neither. Natch." He winked. "Knuckles? You tired?"

"Yes."

Sonic looked strangely deflated at the admission. Knuckles didn't add his doubts as to whether he'd be able to rest here, regardless of weariness.

"Oh," said Sonic. "Well there we are then. We stop for a kip. It's been a long day after all." He frowned. "Or… has it been a day? Less? More? It's… weird."

Knuckles looked around doubtfully. "Is it safe here?"

Sonic shrugged. "Safer than falling asleep and then into a bubbling pit of chaos-knows-what, or fighting whatever all these extra bots are building up to, with everyone strung out, yeah. We can take turns. I'll go first."

Knuckles considered objecting but instead lay down. He might not be able to sleep, but he could rest. Could slow his breathing and relax his limbs and empty his mind. It wasn't easy. He was far, far further from home than he should be and everything felt wrong, but he could put it aside, after a fashion and rest.

He wasn't sure how long it was when he heard Sonic approaching him again. He sat up.

Sonic blinked at him. "Were you even asleep at all? Or have you got like super guardian-ish senses for waking you up if someone gets too close?"

Before Knuckles could decide on an answer Sonic had raised his hands. "Right, no ask-y questions about guardian-y stuff. Got it."

Knuckles hesitated.

"I was awake."

Sonic gave him a thoughtful look but didn't ask whether that meant 'already' or 'all the time'.

"Okay," he said instead. "Wake Tails when you get too sleepy. Tell him to wake me after an hour."

Knuckles nodded, not sleepy in the slightest. He felt better sitting up. He was still resting after all. Watchful but still. Calm in the absence of any immediate threat but alert enough to be safe from any that should come. He wasn't home, the Master Emerald was not at his back, but even so it was there at the edge of awareness. In the quiet he could find it. Soothing. Familiar. Restful. And there was something familiar too about this sitting, and waiting, and watching.

He didn't wake Tails, and eventually Sonic stirred first, hours later. Blinking awake in the not-daylight of the florescent lighting. He rolled over onto his hands and knees then sat back on his heels before getting to his feet.

"You didn't swap." Sonic looked puzzled, almost worried.

Knuckles stood and stretched. "I wasn't sleepy."

"You said you were tired." It sounded almost like an accusation and Knuckles frowned.

"I was. But I wasn't sleepy. And now I'm neither."

It was true, although Sonic shook his head looking confused. Knuckles could feel the faint scratchiness of lack of sleep somewhere behind his eyes, but he wasn't physically weary any more and it would be a long time before he was forced into sleep if he didn't want to.

Sonic stared at him, another question obviously forming, but he bit it back.

"Your call." He turned away. "Hey, Tails, wakey wakey."

Tails mumbled and blinked and wriggled his way awake and sat up looking at them.

"I didn't take a turn," he protested.

"No need," Sonic grinned. "You're up first next time, okay?"

Tails nodded. "So are we hitting the computer centre?"

Sonic nodded. "We can't be far, the security was getting tighter every step until we stopped. I'm amazed we didn't get found in here.

"Nothing in here worth guarding," Tails guessed aloud. "Everything's empty."

Sonic nodded. "For now. Best move before they decide it needs filling up!"

Tails bounced to his feet. "I hope there's breakfast they next place we end up."

Sonic grimaced. "Yeah. I could eat a whole trolley of chillidogs."

"Not for breakfast!" Tails laughed.

"Absolutely for breakfast!"

"Can we move?" Knuckles had only realised how hungry he was himself when the discussion had started and he could have done without it.

Sonic glanced over. "Sure. Let's go!"

And they were running again, back on the pipes and up and over the now variously coloured chemical vats beneath them, until without warning the pipe they were currently occupying trembled violently in time with a deep rumbling sound from somewhere above.

Sonic looked around, as he came to a hasty stop. "That can't be good."

Knuckles dropped warily into a crouch ready to fight or run or jump, or for a plunge into the liquid beneath them. Beside him Tails looked ready to leap into the air and Sonic was crouched in a pose Knuckles was learning to associate with the most rapid of acceleration.

He didn't have more than a split second to assess it though because Sonic was already moving and so was something else and Knuckles was tumbling backwards as Sonic had rammed straight into both him and Tails, shoving them out of the way of a huge ball-like machine. It plunged into the vat below the current set of pipes they'd been manoeuvring on and Tails shot into the air with a wail as he was splashed.

"Ow! That stuff does sting!"

The robot launched upwards again, this time encased in a film of the stuff.

"Tails, are you okay?" Sonic shouted, warily watching the device manoeuvre.

"Yeah. Tails scowled down at it. "Be careful."

Before anyone could answer the was a sharp zap and the film of chemicals splattered away from the device. Knuckles flung himself flat to avoid it and found his faces inches away from a vat of the stuff. He jumped back to his feet. Sonic and Tails had also managed to dodge and Sonic was again crouched to leap. Knuckles gave him a half second head start to avoid any repeat of the fiasco in the hills then followed him into the attack.

Three blows from three separate directions rocked the device as Tails also dropped down on it from above. It dived down into the pool of chemicals, circling like a shark.

"Don't get-"

"—above it. I can work that out for myself, Sonic!" Knuckles snapped.

"-caught up on it," Sonic corrected, circling in the opposite direction to the device. "Get dragged down into that stuff and it's not going to end well."

Knuckles nodded sharply then leapt further clear as the robot surged up into the air once again, splashing chemicals as it went and thumping down hard enough to make the pipe shake and Sonic stagger as he launched himself. He glanced off doing no real damage and landed reeling. Knuckles flung himself forward, pushing Sonic clear with one hand and swinging for the device with the other. Tails gave it a strike in passing and ricocheted off, recovering himself in the air and grabbing Sonic in the same movement. Scooping him into the air to attack from above.

Caught top and bottom the device cracked apart with in a brief flower of strange coloured flame that burned out almost before it had registered on Knuckles' vision. He jumped back, in case of left over chemicals, or toxic smoke but Sonic and Tails seemed unconcerned, already celebrating.

"That must have been guarding something important."

Tails ran off the pipes back onto a heavy metal walkway. The chemicals in the vats here were viscous, gel-like, even rubbery, though they stank just as evilly. Tails eyed a hatch in the floor.

"Down there?" Knuckles asked. They hadn't had much luck heading downwards in this place and the thought of those chemicals, however inert they seemed right now, pouring in on top of them was not a pleasant one.

Sonic gave the hatch a kick.

"Unless you've got a better idea!"

He leapt down and there was a startled yelp and sound of a struggle. Tails and Knuckles gave each other an alarmed glance and dived in after him.

Sonic was standing gaping at them open mouthed when they landed.

"Eggman was right here!" Sonic waved at another hatch in the floor. "But he had another way out. Went off like a rocket. No following without getting toasted."

Tails was beaming. "You panicked him enough though. Literally everything on here is still logged in, still open!

Tails jumped up onto a seat at the system, feet dangling almost his own height off the floor, his face full of fascinated delight.

"Oh this is weird!"

His tone suggested this was a good thing and Knuckles frowned at Sonic who smiled and shrugged, and jumped up beside him.

"What's weird?"

Tails pointed.

"Blobby things," said Sonic. "Yep. That's weird."

Tails giggled. "They're not blobby things. They're… I'm not sure. They're just a visualisation of something else I think. Atoms or molecules or lattices or something. He's building something at a microscopic level, building something or growing something. And I can't work out if it's a chemical or a crystal. It's… weird. And it keeps changing."

"Whatever they picked up back on Knuckles' island was sort of crystally." Sonic leaned in curiously. Knuckles moved around to look at what they were both was staring at but had to conclude that Sonic's description of 'blobby things' was about all he could make if it.

"So you don't know what it is, or what it could do, or how it explains anything that's happened to us?" Knuckles asked.

Tails' ears lowered. "No. Sorry."

Sonic shrugged. "Was worth a try. Let's get out of here then."

Knuckles peered down the escape hatch Eggman had taken.

"Looks clear now."

Sonic jumped off the tall seat to join him, and Tails followed after a moment, with a reluctant glance back.

"These things move pretty fast," Sonic warned Knuckles.

"Good. The sooner we're out of this place the better."

Knuckles didn't wait for further comment, but leapt into the tube, closing his eyes as the systems caught him and whisked him along, fast enough to take his breath away once more.