This is the sequel to "Hey Satan, Paid My Dues". To understand this story, I do recommend you read the prequel first. Also, like the prequel, the title is taken from AC/DC's "Highway to Hell".

I do not own Supernatural, and I hope you enjoy!

Dean panted as he ran through the forest, eyes and flashlight flitting frantically from broken branches to giant paw prints in the mud slowly filling with rain. Ahead of him - about half a mile, he guessed - a howl broke out, different from the others he'd been hearing for the past half hour. There was a tone of success to it, high and happy instead of deeper frustration. Baying as he ran his target down. The elder Winchester skidded to a stop, mud flying under his boots as he switched directions to keep following the trail, pushing himself faster than before. A few minutes later, Dean burst into a clearing and nearly collided with a large, black, whip-like tail. Arms wheeling, he attempted to stop and veer away at the same time, and ended up falling gracelessly into the mud. Groaning, he wiped away what had splattered in his face and glared, reaching out to shove a huge muzzle away before drool joined the mess. "Yeah, yeah, laugh it up, Sammy," he grumbled. The hellhound backed up, tail wagging and a grin seemingly stretched across his face.

'Dean!' Sam thought, tongue hanging out and drooling happily now that his Pack member had arrived. 'Dean! Dean!' He waited impatiently for the hunter to stand up again, and then rushed towards the other end of the clearing.

"Woah! Where're you going, Sam?" The elder Winchester called, jogging after his brother. Only when the hellhound pulled to a stop did he notice that the forest didn't become denser like he thought, but disappeared altogether in favor of a rock face and a dark cave opening, hidden in the shadows until they broke up under his flashlight.

'Inside! Prey inside!' the hellhound barked - not that the hunter could understand. Resisting a growl of frustration, he instead opted to rush the cave entrance, circling once before dashing back out to his Pack. Tilting his head, he stared up, begging that he had been understood.

Dean looked at the cavern, then down at Sam. "Only you could still manage puppy eyes after being turned into the biggest hellhound I've ever seen," he sighed, and got what he could only describe as a cocky grin in response. He grinned back as he remembered what Cas had said - that Sam would never be human again, but had likely kept his memories and would, over time, be able to understand humans again. He had been doubtful, after the tongue bath he'd received when they first reunited, but he couldn't deny that at times like this Sam seemed more and more like himself again.

"Alright. Come on, Sammy! Let's go burn that son of a bitch." The hellhound barked in reply, dashing to the cave entrance and circling it as he waited for his Pack member, and then padded into the dark lit only by the light Dean held in his hand. Only a few feet in, Sam paused as a peculiar scent reached his nose, different from the decay and mold he'd tracked through the forest, and -

Dean jumped as a sound he'd never heard before echoed through the cavern. He whirled around, searching for the source, before he realized the sound had come from slightly lower. Looking down, he saw Sam had his nose scrunched up, eyes watering, before making the same sound as before, his body shivering from nose to tail as his head bowed. He stared uncomprehendingly for a second, trying to figure out what it was, before laughing, thankful they weren't too far into the tunnel yet that he could.

Sam huffed, scraping at his muzzle the best he could with his paw in an attempt to get rid of the scent and, when that didn't work, doing his best to focus on the original scent so he wouldn't sneeze again, all the while glaring at the bunch of flowers growing on the cave wall.

It didn't take long to find a place where the tunnel widened into a proper cavern. Dean rushed towards the body hanging from the ceiling, checking for a pulse, and bowed his head when he couldn't find one, eyes connecting with Sam's as the hellhound let out a whine. "Too late for this one, Sammy," he sighed, looking up to scan the room. "But we can kill it before it takes anyone else." There was no reply, and when he looked down again he only had to see the bared teeth, narrowed eyes, and ears pulled back to jolt around, staring at where the tunnel continued.

Sam growled, crouching low to the ground as he maneuvered around his Pack to get between him and the now fresh smell of decay and mold. The scrape of claws against the stone floor was the only warning he had before a large, humanistic shape hurtled towards him, eyes firmly fixed on the hellhound's Pack.

The wendigo emerged from the dark, fully visible in Dean's flashlight's beam and ignoring the flare gun he aimed at - "SAM!" he screamed as his brother hit the monster head on, jumping out of the way as the pair rolled and forced him back into the tunnel they had come from. "Sammy, get out of the way!"

Sam lashed his tail, cat-like, as he tried to get a firm grip on the wendigo with his teeth. Blood, a dark gray, welled up from scratches his claws had made in the thing's sides. Vaguely aware that they were grappling close to his Pack, he went a different route as he released the wendigo and tried to drive it in the opposite direction.

Dean's arms wavered, trying to find a good opening behind the giant mass of fur in-between him and the monster to release the flare, when suddenly there was a howl of pain, blood spattering against the floor, and seemingly no Sam.

The hellhound felt the wendigo's own claws easily rip into his side and immediately followed his instincts - to protect his injured self, and to not be a visible reminder to his Pack that they had a hurt member to worry about, he turned invisible. Slinking to the side, he slid heavily down the wall to lay on his uninjured side, panting from the exertion of the fight and the pain, and watched through slitted eyes to see if he would need to intervene to save his Pack.

It took a few seconds for both Dean and the wendigo to recover from the shock, and when they did the monster turned towards the elder Winchester. Praying his younger brother had moved out of the way, Dean pulled the trigger and watched, relieved, as the wendigo went up in flames. Turning to where he thought his brother was, judging by the blood trail, he asked, "Sammy? Can you make yourself visible again? I need to see and treat that wound."

The hellhound let out a whine, wanting to deny his instincts and help his Pack, but he didn't have the energy and, as his claws scrabbled against the hard rock ground trying to get a grip so he could stand, the pain and blood loss became too much and he passed out.

Dean barely detected a noise from the side of the cavern and hurried over. Kneeling a few feet from the wall, he reached out a hand and pressed it to a warm, furry side wet with blood. Cursing, he asked again, "Sammy? Visibility would be awesome right now." He managed to wait thirty seconds and then, with no response, guessed his brother was unconscious. "Great," he sighed. "How am I supposed to treat a giant, invisible, unconscious hellhound?"

It took awhile, but Dean didn't think there were any serious wounds besides the ones on Sam's side that, thankfully, the hellhound wasn't lying on. Bandages had cost him both his flannel and undershirts, but in the end he stemmed the blood flow enough that Sam would, hopefully, be able to make it back to the impala without starting to bleed out again. Once there, he'd be able to stitch his brother's wounds.

"Sammy?" The hellhound heard his name through a haze. "Sammy, wake up." A hand shook his shoulder, and the smell of motor oil copper gunpowder burning rubber surrounded him. "I can't carry you ten miles to the impala, you have to wake up and walk." It was the scent of Pack - of safety. Sam opened his eyes and, whimpering from the pain, made himself visible again.

Dean sighed in relief as his brother appeared in front of him and his eyes opened. Petting his flank while carefully avoiding the temporary bandages, he whispered, "Good job, Sammy. Can you stand up now? I know you want to sleep, and you can soon, but I need to stitch you up first and the material is all in the impala."

The hellhound whined at the thought of standing right now, but his Pack needed him to. Plus, he'd much rather recover in their den than in this strange, decay and mold stinking cavern. For the second time in less than an hour, Sam's claws scraped against the rocky ground in an attempt to find enough leverage to stand. This time, though, Dean immediately leapt to his aid. With his Pack bracing his injured side, the hellhound managed to find his - admittedly unsteady - paws. Listing sideways against the wall, panting from the effort, and holding back a whimper at the throbbing pain in his side, Sam butted his head against Dean's thigh in an attempt to ask 'what now?' His Pack let out a breathy laugh. "Home, Sammy. Come on." The hellhound would have grumbled if he could, but he slowly moved away from the wall and, with Dean's arm around his shoulders and his hip and thigh steady beside him, the two brothers walked towards the tunnel.

Between Sam's nose and Dean's experience it had taken a little more than an hour to find the wendigo's cave. Now, with the elder brother emotionally exhausted and the younger severely injured, it took three hours to reach the road again. Once they did, Dean slowly lowered Sam to the ground, not sure if he should be worried or not that the hellhound didn't whimper once at the change in position. Deciding there was nothing he could do besides what he'd already planned, he hurried to the impala's trunk, fetched the medical kit, and before his brother even knew what he was doing gave him a sedative. "Sorry, Sammy," he whispered. "That should keep you out just long enough for me to stitch you up, and then you can sleep for real, 'k?"

The slide into consciousness was easier this time, Sam decided. Less of a fog to fight through, and the leather gas musk burning rubber of the den mixed with the motor oil copper gunpowder burning rubber of Dean to create a potent mix that cut straight through the scent of his own blood. Paws sliding in the dew covered grass, Sam growled at the effort it took to scramble upright and propel himself towards the den.

Dean woke from a doze at the sound of growling and quickly threw himself from the driver's seat into the way of the charging hellhound. "Woah, Sammy!" he cried, hands held out placatingly. "Slow down, ok? Let me at least get the door open first. And don't just jump in like you normally do, you could tear your stitches." The look he received in reply could only be described as Sam's bitch face and Dean, sighing, got out of the way at the same time he opened the back door to the impala.

The second his Pack was clear of the den entrance Sam hurtled forward, lowering his head at the last second and pushing off with his hind legs to clamber onto the seat. He sniffed around as best he could, given that he had a hard time turning around when he was uninjured, and plopped down onto the nest of blankets and towels Dean had thrown over the leather. Letting out a heavy sigh, he wagged his tail once, looked up as his Pack entered and closed the den doors, closed his eyes, and relaxed into sleep.

Dean drove for several hours before there was any sign of Sam waking up. Glancing in the rear view mirror at the sound of a yawn, all he could see for a second was the long, razor sharp teeth the hellhound flashed - and then the jaw clicked shut, the head shook, the ears flopped, the lips smacked, and the entire scene transformed from a terrifying view to the picture of adorableness. At this thought, Dean groaned and shook his own head, "You've corrupted me, you know that?" All he got in reply was a sideways glance and a tail thumping against the door as the hellhound tried to stand. "Woah!" Dean cried out, slowly coming to a stop on the side of the road and turning around to glare properly. "Sam, what are you thinking? You've got a ton of stitches in your side and you're too tall to stand up in the 'pala even if you didn't."

Sam met Dean's glare head on, widening his eyes into what his Pack called his "puppy eyes", and walked his hind legs over to his fore legs as far as they could go before stopping as the new position pushed his head into the ceiling. To get his point fully across, he pressed his nose to the window before facing Dean again and letting out a whine. This earned him a jaw drop, and Sam panted around a doggy grin in satisfaction. "You want to stick your head out the window? Seriously?" The hellhound barked once and pushed his nose into the window again.

"Alright. Fine. But I get teasing rights forever for you being the only hellhound to ever think about, let alone enjoy, sticking your head out the car window," Dean warned, and pressed the button to lower the glass as he pulled back onto the highway. A rhythmic thumping began, and looking in the rear view mirror proved his suspicions - Sam sat pressed as far into the corner as he could go with his bulk, head out the window, tongue and ears flapping in the wind, and tail wagging up a storm against the seat. Chuckling, Dean turned his attention back to the empty road ahead of them, upped the volume on the radio, and prepared to enjoy the rest of a good old fashioned road trip with his younger brother.

It didn't take long after that to reach their destination. As they pulled up a long, dirt drive Sam barked happily as a familiar scent reached his nose. He knew it from somewhere, but couldn't place the whiskey motor oil paper ash. Dean glanced back at him as the den slowed to a stop and asked, tone hopeful, "You recognize this place, Sammy?" The hellhound barely spared his Pack a glance as he panted, drawing in big breaths of the scent in an attempt to figure it out. It almost reminded him of the den and Dean, as if the source was also Pack.

Dean got out of the car hesitantly. He'd called ahead, but hadn't managed to say that Sam was back, let alone a hellhound. "Dean?" a voice called. "That you, boy? Since when did you have a dog?"

Taking a deep breath, Dean called back, "Yeah, Bobby, it's me. And uh… it's a long story."

The door opened, and he watched as his surrogate father stepped onto the porch. "Considering that looks a hell of a lot like a hellhound, I'm all ears," Bobby replied, eyebrow raised.

Dean opened the back door of the impala slowly, trying to limit Sam's space, and reached for his scruff to try and hold him back, just in case his brother took the older hunter for a threat, and -

The minute his Pack opened the den, Sam bolted as fast as he could, shouldering his way through the crack and dashing towards whiskey motor oil paper ash, the burning pain from his injured side a minuscule thought in the back of his mind. 'Pack!' he barked happily, thundering up the steps to circle his newly found family member, nosing his legs and giving rapid licks to his hands in-between barks. 'Pack! Pack!' As the hellhound started to get dizzy from all the whirling, he pounded back down the stairs to Dean, reared up on his hind legs, and gave him the best hug he could, panting happily in his face. 'Thank you! Thank you! Pack! Safety! Pack! Thank you!'

"Woah, Sammy!" Dean laughed, wrapping his arms around the giant hellhound in his arms to steady them both. "Careful there, buddy! Stitches, remember?" he asked, leaning around the furry head to make sure his side wasn't bleeding. "Looks good, but still, you know better," he scolded.

"Dean?" Bobby asked, surprised and happy that the man he saw as a son was much better than when he'd last seen him, but confused as well. "Why do you have a hellhound named Sammy?"

The elder Winchester glanced over at the older hunter, who had followed the hellhound off the porch and was now only a few feet away. "Uh… Cas broke Sam out of the Cage but couldn't bring him back human so now he's a hellhound," he said quickly.

Bobby choked, stumbled, and reached out to steady himself on the closest surface - which just so happened to be Sam, who immediately turned his face towards Bobby's, panting happily through a doggy grin. "This is Sammy?" the older hunter asked thickly, blinking away tears. "You're sure?"

"Cas told me himself, and he certainly acts like him. More carefree, but then he is a dog," Dean grinned.

"Yeah, he is…" Bobby whispered, smiling as he reached out to scratch behind the hellhound's ear.

Sam leaned into the touch of whiskey motor oil paper ash, or Bobby as Dean called him, before pushing off of his Pack to fall back to all fours for a second before turning and plopping down across their feet. It would be better if feathers wind sun silver was here, to complete the Pack, but he would pop in that night to check on them like always. Until then, Sam fully intended to relax and heal, safe in the knowledge that no one could take advantage of his weakness without first going through Dean or Bobby - without doing the impossible.

I may write more (and I did try, but this was the extent my writing spree took me on). I hope you enjoyed, and please review!