Hi, I got the idea for this story from the kink meme, here is the prompt:

Porthos has a nightmare and Aramis attempts to wake him up... not a smart move. Porthos doesn't take kindly to being surprised and reacts aggressively. Not realising it's Aramis, he either punches him in the face or strangles him (or both). Up to author what happens next, maybe Athos walks in and has to pry Porthos' hands off Aramis' neck. Porthos, realising what he's done feels terrible but Aramis refuses to let him blame himself.

Enjoy :)

...

It was quite a blessing, Aramis had thought, that he and his two brothers had rooms right beside each other, with Porthos' in the middle. As he released his right hand from Porthos' wrist to grab the brass candlestick on the bedside table, he knew that if his idea did not work, he was going to die. He took the candle stick and threw it against the wall with as much strength as he could muster while being choked. It made a noise he hoped would wake Athos up and he returned his hand to Porthos' wrist in an attempt to once again pry his hands off his throat.

Porthos was a strong man, there was never a single doubt about that. Yet even in their sparring practices Aramis had not once felt the full power of his brother. Looking back at the incident, he was most certainly in the wrong. Porthos was always a peaceful sleeper so Aramis had been alarmed when he'd stepped into Porthos' room to find his face distressed and a thin layer of sweat on his forehead. Naturally, Aramis had moved closer to shake his brother awake. After Porthos didn't budge and continued to groan, Aramis had assumed he was having a nightmare. So he'd done what Porthos had always done when the scenario was reversed; he gently cupped Porthos' face to wake him slowly.

Unfortunately for Aramis, there were two things working against him that night. The first, and most important fact of the night was that it was very dark in the room. The overcast sky was letting very little moonlight in. The second was Porthos' speed. For someone who was half asleep, Porthos' arms came up surprisingly fast, much like a pair of snakes that had been waiting to strike. Of course, in the first second of being strangled by his brother, Aramis remained as calm as he could. He moved one hand up to Porthos' right arm and the other to his shoulder to pat it gently in a message he thought would be interpreted as, 'it's alright, it's just me.'

Porthos' eyes were open and angry and when Aramis patted his shoulder he growled and tightened his grip. That was the moment Aramis had started to panic a little. He grabbed both of Porthos' wrists and tried to yank them away but his strength was not even a tiny bit close to Porthos'. It never was.

The moment Aramis started to panic a little more was when he had tried to say Porthos' name but all that came out was a soft squeak. His throat was no longer pulling air into his lungs and he was starting to see little black dots in his vision. For a split second he was distracted by how they danced around the room as he looked for something, anything, to hit Porthos with.

The instant his eyes focused on the candlestick in the dark, he knew that he was not going to try to knock Porthos out with it. Even with his life being threatened, Aramis could never do that and was sure it would not even work considering his weakened state. So, he'd opted to throw it against the wall and hoped Athos was there and would come investigate. Aramis was beginning to lose consciousness and started to panic. He didn't want to imagine Porthos waking up properly and coming to his senses with Aramis lying unconscious on his bed. He wondered if Porthos would stop if he just stopped trying to get his hands off his neck and relaxed, play dead in other words. He didn't have time to try his experiment however, as Athos opened the door in that moment with half asleep eyes and a frown on his face. Aramis strained to look at him and vaguely noticed that the black dots had grown significantly.

With a full body jolt, Athos had obviously realised what was happening and dashed over, yelling at Porthos.

"Porthos! Porthos stop!" He yelled, his voice uncharacteristically panicky as he tried with all his strength to pull at Porthos' hands, "Stop it! Let go! Porthos, you're going to kill him!"

Aramis' eyes were beginning to droop and, just before Athos punched Porthos in the face, he thought in that moment he was actually going to die, by the hands of his brother. Porthos startled from the punch with a grunt and let go, releasing Aramis and causing him to topple to the floor.

Through the sound of his own coughing and the pounding in his head, Aramis was very vaguely aware of Athos' harsh breathing and wondered worriedly if Athos had had a panic attack. He felt a hand rubbing his back and someone telling him to breath. Aramis registered that it was Athos' voice and did his very best to breathe as deeply as he could, even though his light headedness was getting much worse.

"What…?" He heard Porthos' voice from behind them and heard him get off his bed, "Did someone punch me?"

"Yes." Athos answered sharply.

Aramis cringed. Athos should not be angry, Porthos would never do something like this deliberately.

"What's going on?" He heard Porthos say, "Aramis?"

He could hear Porthos step closer but could not register much besides the pattern of the wood on the floor which his cheek was resting on.

"Athos?" He heard Porthos say again, "What's going on? What happened?"

Aramis felt Porthos touch his shoulder and closed his eyes.

"He's passing out, lets get him on the bed."

Athos' voice was the last thing Aramis was aware of.

…

Aramis woke up with the feeling that someone was staring at him and it made him a little uncomfortable. He didn't open his eyes and kept very still. He was aware of the sounds of birds and realised it had to be morning. As the memories of what had transpired came back to him, he wondered if it had all just been a ridiculous dream. He opened his eyes slowly to allow them to adjust to the light and realised he was lying in Porthos' bed.

Upon waking up properly, he felt that his head was pounding with determination and he also found the source of the staring. Porthos was sitting in a wooden chair about a meter from the bed. He looked… unwell. His eyes were bloodshot and his skin pale. He was on the edge of his seat and was staring at Aramis as if he were about to sprout a pair of wings.
"Mmm… P'ths?" Aramis croaked and realised with a sharp pain in his throat that what happened was no dream. His hand went to his neck where he felt a bandage. His throat was aching and he grimaced slightly though did not move his eyes away from Porthos'.

Porthos stood up and walked to the bed. He very lightly moved Aramis' hand away and looked into his eyes.

"Don't touch it, and don't try to speak." He whispered, his voice straining under careful control.

Aramis gazed at him, taking in the red in his eyes and the way his hand shook violently as it made contact with Aramis' own. Just as Aramis reached out to take Porthos' hand, his brother pulled it away and strode out of the room, closing the door behind him. Aramis heard his footsteps recede until there was silence. Then he heard a brief muffled conversation of raised voices and then silence.

For some reason, Aramis felt incredibly alone. Just as he yanked the blankets away and swung his legs over the bed, ignoring his pounding head, Athos marched into the room, leaving the door swinging behind him.

"Don't you dare." He said and lifted Aramis' legs back on the bed and tucked him back in forcefully.

Athos gave a strained smile and said, "No speaking for you, therefore no arguments."

He continued to tuck Aramis in unnecessarily and stopped only when Aramis grabbed his arm. They made eye contact and Athos seemed to deflate a little.

"I'm sorry…" Athos whispered, "I could not get him to stay. Nor could Treville."

Aramis' heart started to pick up speed as the words sunk in. Athos read the confusion on his face and went to retrieve the chair to pull it closer. After sitting in silence for a few seconds he looked at Aramis with a forlorn expression.

"After what happened… do you remember what happened?" He asked.

Aramis nodded and Athos continued, "After what happened, Porthos became extremely distressed. I had to force him to drink a cup of wine to calm him down. He stayed here the rest of the night and watched over you with me. I couldn't console him. You and I both know he had no idea who he was attacking."

Aramis nodded again and straightened in the bed. Athos eyed him for a moment and continued.

"He wouldn't listen. He just sat in this chair all night."

'Crying.' Aramis thought, his heart sinking. It was plain to see on Porthos' face.

"Early this morning," Athos said, "He left the room after gathering his belongings. He handed his uniform to Treville and left the rest of his belongings outside this door, ready to leave as soon as you woke. There was nothing Treville or I could say to make him stay."

Alarmed, Aramis yanked the blankets away again and tried to climb out of bed.

"Aramis! No!" Athos said after leaping from his chair to pin him back down.

Aramis fought against him with all his strength and managed to get out a gruff of protest.

"Aramis, look at me!" Athos yelled and Aramis stopped his struggling to obey.
Athos' eyes were sad but there was a tiny hint of fondness in them, "We will go after him, alright? We will, I promise. Just not right now. He needs space and you need to get a little more strength in you."

Aramis was getting angry and pointed to the door in frustration, mentally pleading with Athos to understand that Porthos could be heading anywhere in that moment, further and further away from them.

Athos shook his head and smiled, "I have a feeling where he's heading to. Did he say anything to you?"

Aramis shook his head, still pointing at the door.

Athos sighed and gently patted Aramis' arm so that he would relax. He let it drop but he was still fuming and breathing deeply.

"He'll probably head to the Court. To Flea." Athos said.

Aramis narrowed his eyes and frowned in disagreement.

Athos raised his hands to pacify him, "Think about it. He's angry with himself and he's upset about what happened. Eventually he will miss us. Besides, you are hurt. Porthos will not stray far knowing that you might need him. He will wait and probably monitor you somehow, from a distance, to make sure you're alright before he leaves somewhere. If by that time he still wants to leave of course."

Aramis huffed. He didn't like the idea of Porthos going back to the Court but he could not deny that Athos had a point. If it had been the other way around, he would also want to make sure that Porthos was absolutely alright before properly leaving. He glanced at the bit of the garrison he could see out the window and sighed in defeat.

"Treville has informed me of course that Porthos' uniform will be waiting for him upon his return. Whenever that may be." Athos said reassuringly as Aramis rested his back against the pillows once more.

Athos stood up, "I'll bring you some soup. I can't imagine you'll be able to swallow anything solid."

When Aramis was once more alone in Porthos' room he looked around. There wasn't much in it besides the bed and the small table. The brass candlestick was still lying on the floor where it had landed and Aramis felt a tear escape him. He vaguely wondered what Porthos was doing in that moment before shutting his eyes once more.