Author's note: I needed to start getting this idea written, because it's been plaguing me for about two months now. Shadow is a super difficult character to write for (at least for me), so of course my brain decided he needs to be in this story. Theme is mostly adventure/friendship, with a bit of drama and dashes of humor thrown in. Rating will stay K+ with the potential of a bump-up to T if I'm worried about a scene that's more thematic/violent.

FYI, Mobius and Earth will be used interchangeably, with the notion that it's a fictional Earth that Mobians call Mobius. I was trying to figure out if there was a canonical reference for the games to use, and have humbly determined that even Sega isn't sure about this.

Updates will be much slower this go-around, but perhaps this will give me the motivation to get this ball rollin'. :)

Chapter 1: Shopcrasher

Northern Hemisphere

The taiga was an expansive forest, with the foliage of tall fir trees masking the skies above and blocking whatever little sunlight remained of the day. Adjusting her puffy purple jacket, Rouge clicked on a remote device in her gloved hands, her brow raising appreciatively when the screen displayed a bright light along the map.

"There you are," she purred to herself. Gauging the distance and direction, the white bat pocketed the gadget back into the messenger bag slung around her shoulder. With a quiet flutter she took to the air, her wings barely needing to beat against the chilly downdraughts flowing between the massive tree trunks. The steadily dipping temperature bit at her large, pointed ears, and made her tangentially wish she had worn a beanie. With any luck, however, she wouldn't need to be out here much longer.

A few miles later she perched herself on a thick branch, her vision quickly adjusting to the darkening surroundings. Small tufts of snow covered the lowest reaches of ground, the canopy above preventing even the remnants of warm autumn air from melting it.

A faint blue glow off in the distance caught her eye, making Rouge grin triumphantly before gliding down towards it. Her boots clicked against the protruding rocks when she landed, her hand already sliding open the bag's flap against her side. She stepped around the tall boulder, jumping down into a crevice created by it and the residing hillside.

Something hissed, and she nearly stumbled back at what she saw.

"Wha—?"

There was a loud groan, accompanied by a bright flash, and Rouge's words were sucked away.

Another draft sent dead leaves scratching against the crags as silence and darkness reigned once more.

Mystic Ruins

"Sonic Sonic SONICSONIC SONNNIIIIIIC!"

Like the distant rumble of a train, approaching closer and closer until its horn blared excruciatingly loud and was shaking teeth right out of your mouth, such was the same as Sonic's name being repeatedly called. Originating from what he could only presume was the hangar, muffled thuds indicated multiple items falling in the wake of careless dashing, with a cacophony of pounding up the stairs, and finally ending with the abrupt WHACK of his bedroom door being slammed open.

"SONIC SONICSONIC!"

The sound was shrill up close, excitement bringing it up higher than soprano, if that was possible. Sonic made something akin to an, "Nngh," then quickly followed it up with an "OOMPF!" when the source of the broken record jumped on his bed and, by proxy, the lump that was the blue hedgehog, currently residing between it and a mound of blanket.

"Tails," the lump said.

"SONIC Sonic omichaos you wouldn't believe what I found out, the emerald that we have I was testing it under this new method of reverse polarization and—"

"Tails."

"—so I thought maybe it was a fluke but then I ... I..." The rambling trailed off, albeit slowly, and the two-tailed fox in question sucked in a volley of air, apparently realizing that breathing was still a necessary function of living, at least in this moment of time.

Silence returned once more, aside from some annoying flickies that seemed to enjoy chirping at what the hedgehog considered to be scandalous hours of the morning.

"What's the rule?" Sonic finally asked, calmly.

There was a long pause. "Um ... no television after midnight?"

"No. The other one."

Despite being prone under a pillow and blanket, the kit was still sitting on top of the hedgehog, so Tails' fidgeting was distinctly noticeable in the span of his deliberate silence before answering. "Uh, to not ... not to wake you with epiphanies before noon."

"And what time is it?" Sonic prompted, still unmoving.

If cringing could be a sound, the hedgehog definitely heard it. "It's, well—uh, seven-thirty," he squeaked his answer.

"And what are you doing right now?"

A long sigh came out as the fox slid off the bed. "Waking you with epiphanies before noon," he mumbled.

"All right, then. See you in four and a half hours."

From a sliver of opening within a fold of his blanket, Sonic could see Tails' snail's pace retreat, his big ears flat against his head, and his normally spritely tails dragging across the floor.

The hedgehog rolled his eyes.

As the fox reached the doorway, he hesitated, turning to look back at him. "Sorry, Sonic…" he said quietly.

Sadly.

This time the big sigh came from the lump on the bed, but it was nevertheless followed up with a smirk. "You've been practicing," he told him.

Tails' ears instantly shot up, his appendages thrashing about like nothing was ever amiss. "Pretty good, huh?" he agreed.

Tails 1, Sonic 0.

Sonic found himself groaning as he pulled himself up into a sitting position, the blanket sliding to his lap. "Did you sleep?" he asked instead, stretching his arms and scratching an itch behind his ear.

More awkward silence was the only answer Sonic needed on that front. A glance in the direction of Tails showed the kit toeing the ground shyly.

"All right," Sonic grumbled, shoving the covers to the side and bringing his feet over the edge of the bed, "gimme five."

Like the flip of a switch, excited Tails was back. In a slurry of words that had some semblance of comprehension (namely that he'd be downstairs in his workshop; that, or a dwarf swamp), the fox beelined it out of the room, Sonic's door swinging back into the wall with a slightly quieter whack.

Slipping on his shoes, Sonic jumped out of bed, hopping back and forth to stretch his legs. "Five minutes," he said to himself with a smile, "should be enough to lap the ruins a few times."

Once again, the old wooden door of Sonic's room reverberated as it banged shut, shaking the walls of the house as the speedy hedgehog zoomed outside for his (reluctantly) early morning jog.

Tails was hurrying back and forth from his computer screen to the red Chaos Emerald, currently glowing calmly atop his workbench. Multiple wires exuded from the gem, attached via electrodes, and led into the terminal itself. The little fox's monitor was spitting out characters at an alarming rate, but he quickly deciphered the information as it was presented, and responded to it by typing commands in turn.

A second monitor nearby displayed a map, and was currently showing most of the world in one view, four distinct dots glowing rhythmically and brightly in certain areas along the radar display.

Despite the setup, however, Tails was frowning fiercely, going back to the Chaos Emerald to make adjustments to the electrodes, then back to the computer to change the settings. His manipulation was in vain, however, as the four dots on the screen did not change and continued to pulse as before.

It wasn't surprising, then, that he failed to notice the figure behind him.

After his third trip to the ruby-like jewel, he finally saw a blurry shape in his peripheral vision, his ears naturally turning that direction. "Sonic! About time. Okay, so I think I have a way of finding the other—"

As he spoke, he turned around, and his next words were lost when he made eye contact with the black-and-red-striped hedgehog.

"Sh-shadow?"

Shadow didn't respond, his arms crossed in front of him almost expectantly.

Tails tried again with a hesitant, "Wh-what are you doing here?"

"I need that emerald."

The fox's hand reflexively gripped the aforementioned jewel tighter. "Um, I ... sorry, but I need at least one to power most of my machines. In fact, maybe I can help you! I was working on trying to find—"

"That wasn't a request," he interrupted sharply, cutting Tails' rambling short.

Shadow took a determined step forward, causing the kit's ears to fall back. The silence lingered, and neither moved for a few, long seconds.

Then, in a heartbeat, Tails pressed a button on the side of his worktable, just as Shadow bolted and shoved the fox aside.

The emerald was no longer perched on the desk.

Shadow growled low and turned to face Tails, still on the floor but scrambling back to his feet. "Where is it?"

"Safe," he breathed out, winded from the push.

While he no longer growled, Shadow's teeth were bared, and he turned back towards the fox. In a blink, however, a rush of wind barreled past and the hedgehog was suddenly gone.

A crash behind him, however, told Tails otherwise. Fully standing again, he looked back at the far end of the warehouse, seeing Sonic and Shadow facing one another, with the latter having been rammed into the wall, a nice sizeable dent lining the aluminum partition.

"Hey Shadow, long time no see," Sonic quipped, his stance far more intimidating than his tone. "You okay over there, bud?"

Realizing the hedgehog was talking to him, Tails dumbly nodded. "Y-yeah."

"That's good," he answered, without taking his eyes off Shadow. "Care to explain to me what you were doing?" he asked their uninvited guest.

"I don't have time for this," he said, calmly sidestepping the blue hedgehog.

Sonic followed suit, blocking his path back to Tails. "That goes for two of us, then."

"I need that emerald," he reiterated, glaring at his doppelganger.

Sonic only rested his hands on his waist in response. "So I heard."

"Very well." Shadow rammed into the other hedgehog without warning, sending both tumbling through the hangar with a trail of crashes following each bang or thump of their tumble.

Tails couldn't help but cringe, his hands coming up to cover his ears. "Sonic, stop!"

There was the horrific sound of sharp quills grinding into metal, before the respectively black and blue hedgehogs separated from one another, their stances still defensive and spines bristled for the next melee.

Surrounding them was a majority of the tools, trinkets, and odds and ends of things that had once been stored in the cabinets lining that side of the garage, now nothing more than broken wood and chunks of debris.

The twin tails of the fox agitatedly whipped behind him, hours of reorganizing already clouding his thoughts on the situation. Sonic briefly glanced over and saw the Look, before pointing at Shadow accusingly.

"He started it!"

The black hedgehog had his arms crossed again, but his eyes travelled to the workbench where the emerald had been moments before, obviously biding his time for the next opportune moment.

Tails let out a deep breath, keeping a brave face when he spoke up and instead opted to change the subject. "Why do you need the emerald, Shadow? I thought you had one."

"I did."

Sonic scoffed. "This is feeling like déjà vu."

Tails ignored him. "Look, I can help you find another—"

"Nuh-uh, Tails—!"

"How?" Shadow interjected, still unmoving.

Despite the circumstances, a spark of excitement lit up in Tails' eyes. "Er, reverse polarization of the energies, like sonar but with Chaos energy. Tune it to the right wavelength and the others ping in response."

Sonic, still standing next to the darker hedgehog, raised a brow at his little brother.

In turn, the kit sheepishly rubbed the back of his head. "That was, um, what I woke you up about." Before he could respond, Tails' eyes tracked back over to Shadow and he added, "I had found the rest of the emeralds, but then lost two, and now the other four's energies seem to be mixing with something else, causing really strange interference..." He frowned at that, his mind going back to what he was working on before the intrusion.

Shadow cleared his throat.

"B-but we can help you find another emerald to use—"

"What part of we're not helping—"

"Very well," Shadow concluded coolly.

"—if you tell us what's going on."

Sonic's hands went up into the air exasperatedly. "Glad I can be of use, over here!"

He was ignored again, Shadow taking a step closer towards Tails. Despite his annoyance, Sonic still watched his movements closely.

Their intruder let out what may have classified as a sigh—at least for him—before stating, "Rouge."

"What about her?" Sonic couldn't help but prompt.

"She's missing."

"Since when do you care about anything other than yourself?"

Despite the clear antagonization, Shadow brushed off Sonic's snarky question. He kept his arms crossed as he watched Tails work with the red Chaos Emerald, now back in its pedestal on top of the work desk. Apparently, the base it rested on also served as a locking device, lowering back into and under the table to not only keep it hidden, but to mask its unique energy signature.

Which, he supposed, Tails would of course have.

"And what exactly was Rouge doing with your Chaos Emerald, anyways?"

Shadow didn't reply. His thoughts, however, unwittingly returned to his G.U.N. partner and he wondered—not for the first time—why he let himself get caught up in others' wellbeing.

Adding mind-reading to his list of irritating traits, Sonic quipped, "You really got this misanthrope thing dialed, huh?"

"I'm impressed, Sonic. That was a big word."

Sonic snorted but chose to drop the interrogation. It didn't go unnoticed, though, that the self-proclaimed hero was standing unnecessarily close to him. He was disgustingly munching on some sort of breakfast burrito, as well, probably what he had left to purchase before characteristically interrupting Shadow's plans on acquiring the fox's Chaos Emerald.

"All right, so, I used to have this device a long time ago, where I could essentially hone in on the energy of the emeralds," Tails started speaking, though whether it was for Sonic or Shadow's benefit was unknown. "That distance was limited, of course, which made it unscalable, because we all know that when the emeralds scatter they tend to go across thousands of miles, if not into the Master Emerald's pocket dimensions..."

He stopped his spiel, eyes narrowing in calculation as he stared at his monitor and typed away. Within a few seconds, he continued, "Anyways, since then I've been able to use G.U.N.'s satellites to ping the wavelengths across Mobius, and can at least rule out whether they're in our dimensional time and space."

Next to Shadow, Sonic took another huge bite of burrito, the sound of squelching making him just barely twitch in aggravation.

"Where are the other emeralds," the striped hedgehog demanded.

"Right," Tails quickly geared back on subject, "this morning I had about four—not including this one—located, but their energies were mixing with an unknown wavelength. In fact, it kind of looked like it was—well, never mind, but—"

"Where?" Shadow interrupted more forcefully.

"—but," the little fox repeated, "they've since disappeared, like the other two I had seen earlier this morning."

"And how exactly is that helpful?"

Sonic was now somehow munching on tater tots, each obnoxious pop and crunch of one in his mouth grating on Shadow's last nerves.

"Well, for them to completely disappear off my radar, they would have been called back by the Master Emerald."

"So they're on Angel Island, or your machine is a load of useless technics."

A flash of indignation crossed the fox's expression, but he chose to ignore the comment, most likely remembering its source. He went back to his computer, studying the information on the screen. "I know it's because they were called back," he lightly reiterated, passively pulling up a pop-up window with a scurry of typing. "See? They never moved from their original locations—they just fell off-radar."

Glancing over and seeing Shadow's annoyed expression, Tails hurriedly flipped open his wrist communicator. "Let me reach out to Knuckles, maybe he knows what's going on."

If Shadow appeared annoyed before, the mention of the red echidna soured him to the point of cantankerous. Sonic elbowed him suddenly and he jolted, glaring daggers in his direction.

"Betcha this last taco that Knux will wig out when he hears about the emeralds."

"I don't want your food."

"Hmph. Well then, I bet ya top wing on the Tornado, then!"

Shadow couldn't frown harder if he tried to. "What?"

Sonic rolled his eyes like it was the most obvious thing in the world. "How else are we gonna get to Angel Island?"

"I can't get Knuckles to answer," Tails interrupted them, stepping forward.

The blue hedgehog cracked his fingers together. "Here, let the master try." He opened his own wrist communicator, cleared a frog out of his throat, and hollered (with surprisingly believable fear in his voice), "KNUCKLES, THE EMERALDS ARE GONE!"

He released the button, allowing static to fill the void in its stead. After a few beats he frowned thoughtfully.

"Huh. He must have taken off his communicator. Again."

In a flash, the two-tailed fox was back at his computer. "Here, let me pinpoint the M.E."

"The what?" Shadow asked yet again, with a resounding amount of exasperation.

Sonic scoffed. "Master Emerald. Get with the acronyms, already."

"No one can find the Master Emerald," Shadow calmly stated, ignoring the other hedgehog's jibe.

"I can with a Chaos Emerald," Tails eagerly responded, offhandedly pointing to the item in question. "Again, with reverse polarization, as well as knowing the M.E.'s energy signature (that Knuckles let me collect data on last year), I can zero in on its whereabouts and, by proxy, the island's whereabouts."

One of Shadow's eyebrows imperceptibly raised. His counterpart chose that moment to loudly chow down on his last breakfast taco, barely swallowing before declaring, "All right bud, let's do it to it!"

"That's the stupidest thing I've ever heard."

Sonic looked a trite offended for a millisecond, before covering it with a smug grin. "Grumpus here can take the bottom wing."