This one is set sometime during S12

22. Friendly Fire

Sam quickly salted the doors and windows, throwing another can to Dean who slammed the door to the tiny cabin shut and looked around for something to bar it.

"We are so screwed in here," he growled pouring salt in front of the door.

Cas and their mom stood behind them, both holding onto weapons and glancing around to see if there were any other openings that the demons could get through.

"Why are demons all of a sudden gunning for us anyway?" Dean demanded, throwing the empty salt container to the side as he peeked out the window to look for their pursuers.

"They're looking for information on Kelly Kline," Cas said grimly. "Angels, demons…it's going to be a battle over who gets to the child first."

Sam looked at the angel. "And with Kelly still in the wind, I guess they think we're hiding her."

Cas raised an eyebrow. "Well, to be fair, usually when major things go down in the supernatural community, you and Dean are caught right in the middle of it."

Sam frowned, but couldn't deny Cas was right. Dean groaned and rolled his eyes.

"Yeah, which is just our luck. But that doesn't help us now."

"No, but this might," Mom said, pulling something from her coat that looked like a grenade.

"What the hell is that?" Dean asked.

"It's…" she glanced between them somewhat guiltily. "It's from the Men of Letters. It's supposed to be some kind of magical bomb."

"And it works on demons?" Dean asked skeptically.

Mary nodded. "Yes, that's what it was made for. It shouldn't harm humans."

"Awesome, and the Brits are so reliable," Dean muttered.

Sam glanced out the window and saw more demons gathering, just standing there. He glanced back at the others. "Dean, if it works, we should try it. We're surrounded and there's too many of them for us to fight off without help."

Cas nodded too. "He's right, Dean. I advise you to let your mother use this."

Dean grunted, but nodded. "Fine. But this still doesn't make you working with them okay."

Mom sighed and shook her head. "Alright, get ready."

Sam and Dean took up position on either side of the door and Cas was right behind their mom, ready if demons charged them suddenly. She grasped the door handle and glanced at them. They all nodded back.

The demons watched as they opened the cabin and started forward.

"Come on out, Winchesters," one called mockingly. "We just want to talk."

"Now, Mom," Sam said and his mom pulled the pin on the grenade and threw it.

They all ducked back into the cabin, closing the door and then there was an explosion.

The backlash blew the door in and a puff of dust washed over them, pluming harmlessly against Sam's body as he covered his face.

The demons however, didn't seem so lucky.

Howls of pain and shock came from outside and as Sam dared to look he saw all the demons writhing on the ground, sparking out in agony. The dust from the grenade was settling, forming glowing runes on their bodies. It must have been some kind of spellwork.

"Whoa," Dean breathed. "I guess it did work."

A sudden gasp of pain sounded behind them and Sam and Dean whirled around to see Cas clutching at the side of his neck with a shocked expression on his face before he cried out and collapsed to his knees.

"Cas?" Dean shouted, rushing toward the angel and catching him before he hit his head on the ground.

"Oh god," Sam cried, joining his brother.

"What's wrong?" Mom asked.

Dean peeled Cas' hand away from his neck and Sam's eyes blew wide as he saw what looked like burn marks, and a red glowing brand on his skin just like what had covered the demons.

"What the hell is this?" Dean demanded, and left Cas to Sam's care as he stood and whirled around on their mom. "Did you know this worked on angels too?"

"What? No, of course I didn't; how could you think that?!" Mom cried. "Dean, I would never have used it if I knew…"

"Mom, we know, it's okay," Sam said frantically, holding Cas tightly as the angel spasmed.

"Okay?" Dean demanded. "What the hell is okay about this, Sam?"

"Would you two stop and help Cas?!" Sam shouted.

They finally shut up and crouched next to Sam and the angel. Dean didn't look happy that their mom was anywhere near him but at least he wasn't arguing anymore. And yeah, Sam was pissed Mom hadn't read the warning label, but he knew it hadn't been her fault. It's not like the Brits cared what other supernatural creatures got caught in the crossfire of their missions.

Cas groaned and reached up to claw at his neck again.

"Don't touch it, man," Dean said as he grabbed the angel's wrist and clutched it tightly in reassurance. "Sam I don't even know what this is."

Sam shook his head. "I don't either, but it's not working the same way as it did on the demons."

Cas' eyes slit open and he groaned. "Get—get it off," he managed to grind out.

"We will, Cas, as soon as we find out how," Sam assured him, holding onto the angel tighter as he continued to shudder. He looked closer and saw that the burns on Cas' skin looked like they were being caused by whatever that red powder was, which was not stuck to his skin. "Dean, maybe we do need to physically get it off. Maybe there's a counter potion or something."

"Like a supernatural grease lift?" Dean asked.

"It was a powder," Mom offered. "That may have had all the spell components in it and if we can scrub it off, we may be able to stop this."

Dean was already reaching into his pocket and grabbing his phone. He snapped a quick picture of the strange rune and then stood to go make the call. Sam could tell it was Crowley he was calling, and after a few moments of grumbled threats, Dean closed the phone.

"Okay, Crowley gave me a recipe that might work. I'm gonna go grab the stuff from the car." He hurried out among the dead demons and left Sam and his mom there with Cas.

"Sam, I'm sorry," Mom said.

Sam shook his head. "I know it was an accident, but…" He trailed off as Cas opened his eyes and looked directly at Mom.

"Mary, it…wasn't your f-fault," he ground out. "You did kill the d-demons."

Mom gave him a pained look as she took his hand and squeezed it. "I just hate being responsible for getting you hurt again, Cas."

Dean flew back inside with a bowlful of ingredients and dropped down next to Cas, pouring stuff into the bowl and mixing thoroughly. Then he grabbed a rag and dipped it in the stuff.

He took a breath. "Let's hope this works," he said and started to dab at the burn marks on Cas' neck.

Cas cried out and Sam and Mom both had to hold him steady as Dean worked. It took some doing but eventually the rune stopped glowing and red dust came away on the cloth. They all breathed a sigh of relief. Dean poured the rest of the mixture over Cas' skin to make sure all of it was gone, but once he was done, there was just what looked like acid burns and a mark from the rune that would hopefully heal once Cas started to recover.

The angel breathed easier, and the shudders had stopped wracking his body. His eyes opened and he gazed at all of them gratefully.

"Cas, you good?" Sam asked him.

The angel winced slightly, but nodded, touching his neck gingerly. "It…it felt like it was attacking my grace."

Dean's eyes turned worried. "It didn't do any permanent damage, did it?"

Cas seemed to look inward but shook his head. "No, It didn't work nearly as fast on me as it did on the demons and I only got hit with a little of it."

"Castiel, I'm so sorry," Mom said again.

The angel shook his head. "I told you it wasn't your fault."

Dean snorted slightly and Cas glanced over at him with a firm look. Dean cleared his throat and stood, reaching down to offer Cas a hand. "Come on, let's get you home."

They helped Cas stand between them and guided him out to the Impala. Sam knew they had been lucky this time but he didn't want a repeat of it either. He decided that from now on they would thoroughly check anything the Brits gave them before they used it around Cas.

But right now, they would be thankful they had all gotten out of there alive.