A/N: originally posted on Tumblr for TFrarepairings Fall Trick or Treat 2 challenge.

"Any trace of him?"

Sideswipe bent down to examine the utter lack of tracks left in the ancient dust. "None. But there never was going to be, you know that. When he hides, he hides well."

Sunstreaker grunted in response. His optics were alert, darting from ruined building to hidden alley to gaping dark holes in the street. "Why here, though?"

Sideswipe shrugged. "Who knows? Let's ask him when we catch him, yeah?" He straightened. "Come on. I think he went that way."

Sunstreaker eyed him quizzically. "Why do you think he went that way?"

Sideswipe shrugged again. "Call it a gut feeling. Also, the ground's too smooth that way, too natural." He ghosted ahead, almost as silent as their quarry was supposed to be, and Sunstreaker followed.

-This place gives me the chills.-

-I know, bro. Me too.- Sideswipe moved carefully around a collapsed part of the street. –I know the Autobots cleared this place up, gathered the grey frames and stuff, but I can still almost see them, you know? Hear them, too.-

Sunstreaker suppressed a shudder. He'd been trying hard to ignore the faint humming at the edge of his audial range since they got there. –There's nothing here. The only thing in Praxus that isn't long dead is the mech we're hunting.-

Sideswipe nodded and led them on.

They hadn't gone more than two streets further before he coming to an abrupt stop, though, straightening and turning to stare down the crossing street. –Hear that?-

-Hear what?- Sunstreaker was almost afraid to listen too hard.

-That!- Sideswipe exclaimed. He moved suddenly, darting down the street. –Hear that, Sunny? That's a sparkling!-

-It can't be! No one here's alive anymore, remember?- But now Sunstreaker could hear it too, the wail of a terrified sparkling, and he followed his brother at a dead sprint.

They raced towards the sound, skirting around debris and destruction, until Sideswipe slid to a stop in another intersection. –It stopped? I could have sworn we were right on top of it!-

Sunstreaker looked around warily. –It could be one of his tricks?-

-Nah, I don't think he'd do that,- Sideswipe replied. –It's too cruel, using a sparkling's cry like that.- He threw out an arm, indicating the dead chaos around them. –I mean, there's no one here.-

There was a moan. Sunstreaker's head spun around so fast he almost severed a minor neck cable. –That came from over there!-

-Sunny, wait!- Sideswipe called, but Sunstreaker was already moving. From the scuffle and huffs of exertion behind him, he knew Sideswipe followed.

Again, they ran towards the sound, and again, it broke off suddenly. For a moment they stood there in confusion.

-Let's backtrack, get back on his trail,- Sideswipe suggested finally. –I think this place is getting to me, and I'd like to get out of here as soon as possible.-

Sunstreaker couldn't agree more. He stayed at his brother's side as they picked their way through the rubble, heading for where they'd first heard the noise.

This time, they ignored both the moaning and the sparkling cries. Sunstreaker tensed up every time he heard it, but he clung to the idea that it was a trick, that there was nothing there, that it was a trap their quarry had rigged for them.

But then it got worse.

The trail led through narrow passageways, where Sunstreaker heard clear as day the whispers of 'help me' and 'no, please, don't' and similar pleads for help. Then an open square, where there was a susurrus of unheard voices pressing in on him. Past the ruins of an enforcer station, where the commanding voices added to the din, and then what had to be a sparkling center of sorts. That was the worst, because there there was laughter – laughter that was suddenly cut off and became screams.

It was all there, all at the edge of Sunstreaker's hearing, and he was shivering from it.

-Sides, I can't-

-You can,'- his brother interrupted ruthlessly. –You can, and you must. We'll find him, then get the frag outta here and never come back.-

That was a plan Sunstreaker could definitely get behind. He turned his focus to their path, ignoring the laughter and cries of pain and pleads for help that were only just audible and not audible at the same time. The din wasn't loud, it was right there at the edge of his hearing, but was still a constant presence making his plating crawl and his fingers tremble.

So it was very disconcerting when it just stopped.

-Sideswipe?-

-I know. Don't think about it.-

It was good advice. Not that easy to follow, but good advice.

They headed deeper into the open ruin the trail led across. It had been an official building of some sort – there were still magnificent columns stabbing the air here and there like broken fingers, and underneath the dust and debris the floor was smooth, polished metal.

It was also very, very cold.

Sideswipe stopped, rotating his shoulder. He stared down at his own arm and gave a start. –Sunny? S-sunny, do you see?-

There was hoarfrost forming on Sideswipe's arm, creeping steadily across the plating.

Sunstreaker stared in disbelief. Then he looked down at his own frame.

-Sideswipe, we need to get out of here, or we'll freeze.-

Sideswipe nodded hesitantly, then more firmly. –Right. You're right. Come on.-

They ran. No longer caring about the rubble, or being quiet. No longer worrying about any of it.

Sunstreaker was fighting just to keep the panic at bay.

They crashed through a fence and into what had once been the fabled crystal gardens of Praxus. Now, like everything else, it was in ruins, but even here Sunstreaker could imagine there was more to it than he could see. The crystal shards were gleaming, strange light echoing in them, reflecting a light source they couldn't see.

They pulsed.

Sunstreaker dodged all the crystal shards he could see, scanning wildly for their quarry. He just wanted to find him and get out of there.

Praxus held no place for the living anymore.

-Frag,- Sideswipe swore. He spun in a slow circle at the center of the garden. –The trail ended.-

-It ended?- Sunstreaker knew he sounded frazzled, but he didn't care anymore. He spun with Sideswipe, swords out, trying to keep the city from sneaking up on him. –How the frag did it end?-

-He must be here,- Sideswipe replied, and though he clearly tried to stay calm he was having no more success of it than Sunstreaker. –He must be right here in the garden.-

-Then let's find him,- Sunstreaker bit out, whirling to face a crystal that was pulsing in a particularly nasty shade of orange. The laughter at the edge of hearing got louder.

Behind him, Sideswipe screamed.

Sunstreaker spun, swords already arcing through the air even though he knew they would do no good, only to forcibly stop himself at the sight of Mirage draped across Sideswipe's back, arms around his neck. The red frontliner was standing still, trembling, optics dimmed.

"Caught you," Mirage said with a smirk, and pressed a kiss to Sideswipe's cheek. "That means I win."

All at once, the crystals seemed to dim. The wall of noise pressing at his audials vanished. Suddenly, they were just three mechs standing in the dry, gritty ruins of what was once a place of beauty. All traces of sinister activity were gone.

Sunstreaker dropped down on a piece of rubble and ran a hand across his face. "Primus, Mirage, you scared he life out of me."

"Oh, I'm sorry." The spy sounded contrite, but the look on his face belied him. "Is this place too much for you?" He let go of Sideswipe and came over to sit down on Sunstreaker's lap.

"It was a bit of a trial, I have to admit that," Sideswipe said in a shaky voice. He sank to the ground. "Primus, love, you must have spent ages setting this up. The voices were a nice touch. Damn well scared me to death, and Sunny was even worse."

Sunstreaker sneered, but didn't argue. It was perfectly true, after all.

Mirage, however, looked surprised. "Voices? What voices? I laid out a few false trails and then went straight here. I didn't even have a finalized plan for this until this morning." His slender hand cradled Sunstreaker's cheek. "What voices?"

"The sparklings," Sideswipe said hoarsely. "Crying, and begging for their creators, and screaming in pain."

"Mecha pleading for help," Sunstreaker supplied, clinging to Mirage. "First responders shouting for medics and transports, pronouncing mecha grey and gone, calling for spark support. And that one mech screaming for his brother, did you hear that one, Sides?"

Sideswipe nodded and swallowed. "I did."

"I didn't rig any recordings," Mirage said slowly. "Where did you hear this?"

Sunstreaker shuddered. "Everywhere."

Sideswipe raised his head, looked at their loved. "What about the cold?"

"Cold?" Mirage turned in Sunstreaker's arms. "There was cold?"

"Freezing cold," Sideswipe replied. "I could feel my joints freezing up, I got low temp warnings." He shivered. "There was frost forming on my frame."

Mirage shook his head. "Not me. I don't know what could have done that."

"Primus, Mirage, if you're messing with us," Sunstreaker began darkly.

"Hey." The spy's hands cradled his face again. "If I'd set up traps, I wouldn't lie about it now. I promise I didn't do anything."

"That's not exactly helpful," Sideswipe snorted. "Primus, I feel like I just had a living nightmare."

Sunstreaker didn't reply. He'd stiffened, optics focused on a spot just behind his brother, where a shard of broken crystal was lying against a broken fountain.

It flickered.

He reset his optics. It didn't help. The tiny flicker was still there, a beat of light at the crystal's core, twisted and weak and sickening.

"Sunstreaker?" Mirage frowned. "Sweetling, what's wrong?"

"The crystal," Sunstreaker managed, vocalizer full of static. "The crystal's flickering."

At the edge of his hearing, someone whispered.

Sideswipe darted to his pedes again, staring wildly around himself. "Frag," he cursed. "Frag, frag, frag. Mirage, please tell me you have a ship."

Mirage stared at the pulsing crystals, shaking his head slightly as if to clear his audials. "I do," he said finally. "It's just over there."

Sunstreaker stood as well, pulling the spy in front of him. "Sideswipe, take point."

They moved in battle formation, swords out, defending the less heavily armored spy between them. Sunstreaker tried to ignore the voices, even when they pressed in until they were next to him, tried to ignore the pulsing crystals and the chill in the air and the faint motion at the edge of his visual field. The ice was forming in his joints again, and the pressure in the air was high enough that his head hurt.

Finally, after an eternity, Mirage opened the ramp to the small ship and led them inside. His plating was covered in hoarfrost too, and his optics were blown wide and almost white.

"We're taking off now," he grunted, not even bothering to strap down before activating the controls. Sunstreaker stayed by the ramp, staring out at the restless dead city, until it closed and they were rising through the air. Only then did he join his brother and their loved in the cockpit.

"Look at it," Sideswipe whispered. He was leaning forward, oblivious to the hoarfrost melting off his frame, and staring out through the cockpit windows at the city below.

Praxus should be dark. It wasn't.

Mirage gasped. "It's glowing."

And it was. It wasn't a warm, pleasant glow, not the welcoming shine of city lights. It was darker, more sinister – a sickly green light that barely edged the buildings and made the city stand out from the darkness of the rest of the planet.

"Take us home?" Sideswipe asked softly, optics still locked on the ruins beneath them. "And stay with us tonight?"

"After I've talked to Prime," Mirage said firmly. "I don't know what that was, but I'd like to see the light of the Matrix before I recharge tonight." He muttered something, a litany that sounded half like a sparkling's prayer. "Surely our creator hasn't abandoned us completely."

Sunstreaker moved to look out the side window as Praxus faded away behind him. "Next time we play this game, let's do it on Earth or something, yeah?"

"Or somewhere with living mechs," Sideswipe suggested.

"Or not at all," Mirage replied grimly. "At least not for a very long time."

Sunstreaker agreed completely. He stared out the window until they were back in Iacon airspace, and the glow of Praxus was all but gone.

He tried to convince himself that the chill in the air was just him, feeling cold and tired after the long day. He almost had himself believing it, too.

Until he pulled away from the wall, and saw his own clear handprint edged in an almost invisible layer of frost.

"Yeah," he said slowly, trying to control his own racing spark. "Yeah, let's go see the Prime. Let's do that first. Let's go do that now. Right now."

Later, much later, after a blessing from Optimus, a check-up from Ratchet and more than one worried look from everyone else they encountered, Sunstreaker tried to recharge. Mirage was next to him in the berth, with Sideswipe on the spy's other side, both of them in deep recharge already, but Sunstreaker couldn't. He couldn't.

Stubbornly, he activated the lights again and turned his audials off, before burrowing into the bond and pressing himself against Mirage's back.

There was no whispering at the edge of his hearing.

There wasn't.