Set in the time when Arthur is king, Lancelot is alive, and Mordred hasn't joined the knights yet.

Leon didn't stay as warm as he should have on a patrol.

It wasn't his fault, not everyone is as good as Merlin at starting fires, and since Arthur wasn't on this particular patrol, Merlin wasn't there either. When he and the rest of the the knights with him got back, they were quite ill with bad coughs. Gaius confined them to bed, and fed them nasty potions. It took a few weeks, and his cough wasn't completely gone, but eventually Gaius let him go back to his duties, and by time spring came, Leon thought all was well, his cough had completely disappeared.

He had no idea how wrong he was, the worst was yet to come.

It started slowly, small things, barely noticeable. A little more time in bed, tiring a little easier. A momentarily lapse in concentration here and there, walking into people and walls more often. It wasn't his fault people didn't watch where they were going, and he did have a couple drinks before that incident with the wall... and the door... and the other door.

The difficulty concentrating cane with mild dizziness now. People who never got the better of him while training now got the better of him sometimes. He played it off, saying he had trained them well, or that he was letting them win. He didn't know who he was trying to fool. It was easy to fool them, he was the head knight, his word was respected and believed, but he couldn't convince himself that everything was fine.

He started drinking less, he felt like he got drunk easier, and being drunk felt to much like those little episodes of bad concentration, confusion and weakness.

Paper work was now more difficult, he could read the words fine, but he couldn't remember what they meant, and forgot how a sentence started by time he got to the end of it. Writing a report was getting difficult. The words he needed to make sentences kept escaping him, like figures in fog.

It was definitely noticeable to himself that something was wrong, but he still hid it from others. Whether because of pride, a knight of Camelot doesn't have problems like this, or fear that telling someone would make it real, he didn't know. He intended to tell Gaius, after all he was the physician, but he kept finding excuses. It wasn't really that bad, just a few odd problems that would sort themselves out. A little more time, and everything will be back to normal. Right?

The episodes slowly started getting worse. He noticed a correlation between eating and these episodes of dizziness and fatigue. He liked to eat in his chambers, so he could put his head down for a few minutes afterwards. He covered it up claiming more paperwork. And when he did eat with others, he ate less.

Training got more difficult. Things he could do without a problem before, like running laps around the training field, he now found getting more difficult. He was out of breath easier, and losing more sparing matches. Others started to notice, and joked about him getting old. Maybe that was it. He wasn't really old enough that age should be getting to him, but knights did usually die young. And there had been a lot of stress these past few years, with all the sorcery attacks, and now Morgana. Maybe the stress and his many years serving the kingdom were getting to him.

One day everything came to a head. It started out just like any other day. His servant brought his breakfast to his quarters, he ate, rested, and put on his armour. There was a big celebration for something or another, and big celebrations meant a busy day of competition.

Leon was very busy. As the head knight, he was in charge of making sure things went smoothly. There were jousts and duels and a melee. Leon competed in everything, and since he was a very good knight and won often, he had to keep competing. He didn't have any time for lunch, or resting.

By time the feast started, he was just about dead on his feet. He considered skipping it, but he was hungry, and guest of honour. He also wanted to spend time with his friends, and didn't want them to suspect anything was wrong. So despite a nagging feeling that it was a bad idea, Leon attended the feast.

He didn't drink much, still being weary of getting drunk, but he did eat. He was hungry from all the exertion, and missing lunch, and the atmosphere of celebrating and being around friends made him forget that he didn't like to eat much. The chef had outdone herself, and Leon feasted.

He feasted and he laughed until his sides hurt. When a bout of dizziness made his face almost hit his food, he friends laughed about how drunk he was. They didn't know he only had two cups of watered down wine. When weakness and lapses of concentration made his words slur, they laughed not knowing his mind was perfectly clear and panicking. When he stood up and stumbled because of spots clouding his vision, his friends had another laugh at his expense, and helped him to his bed. They thought it a little odd he got so drunk, but he had been acting odd lately, so they didn't think much of it.

His friends were kind enough to take off his boots and outer clothing layers, and tuck him in bed. Leon was oddly cold, and he was glad of the blankets they put on him.

As he lay on his bed, and heard the footsteps and laughter of his friends recede, he felt the silence envelop him. Being the head knight, his quarters were bigger, and a little thicker walled than most, so he couldn't hear anything.

He couldn't hear any sounds anyone else made, but he could hear his own heart beating. It was unnaturally loud, echoing in his head and rushing in his ears. He could feel his heart beating in his chest, like he had just won a duel, and when he looked at his chest, he could see the blanket on it jump with every heartbeat. That was unsettling, so he tried to focus on something else.

He was still dizzy, so he focused on his breathing, but it was difficult to take deep breaths.

He tried to call out for help, but nothing more than a whisper would leave his lips.

He tried to get up, but his arms and legs were limp, refusing to obey his commands.

He started to panic, and with the extra adrenaline he managed to lift his body up a little bit, only to fall back down onto his bed.

He started panic more, but caught himself. A knight of Camelot does not panic, he assesses the situation and deals with it accordingly. He decided the best way to assess would be to make a list in his head.

1. Something is wrong.

2. Was the wine or food poisoned? Unlikely, poison usually causes stomach pain, although my stomach hurts a bit, it hurts more like being full than poison. And no one else was sick. It's possible I was targeted, but unlikely as it would be easier to poison my personal meals or even my water skin than a feast with so many important people.

3. If it's not poison, is it deadly? Unlikely, my heart is beating strong, and although it is a bit difficult to breath, I am getting enough air without to much difficultly.

4. What should my course of action be? I can't yell for help, and I can't walk. I guess I have to wait until I am able to do one of those, or wait till my breakfast is delivered and ask the servant for help.

With a plan decided on, Leon waited. And waited.

At first he stared at the ceiling, but it was difficult to keep his eyes open, so he let his eyelids drop.

Then he tried to sleep, but the beating of his heart was too loud. So he laid there and thought. Lots of things crossed his mind, some more depressing than others. He thought about life, and death. He always thought he would have a warriors death, he's had so many close calls, surely his luck would run out sometime. He didn't want to die a slow, painful death of illness. With the adrenaline from getting to his room, and panicking gone, he realized he was pain. It wasn't unbearable, but it was quite odd. He couldn't figure out exactly what was hurting. It was his chest, but was his limbs, not his chest, it was everywhere and nowhere at the same time. And even though the pain was bearable, he had certainly had injuries much worse, the pain made him want to scream, or dig his nails and teeth into someone or something. He only didn't because of how weak he was.

He lay like that for hours. Slowly his breathing became easier. Then his heart started beating a little quieter. The mysterious pain dwindle down until it was just an odd memory. He experimentally moved a finger. When he realized he could, he excitedly flexed his arms and legs, only to lose his breath. Once he gained back his breath, he tried again, a little slower.

He slowly sat up, and despite his vision darkening, he stood up. Only to land on the floor. He didn't even remember falling. He slowly crawled to his desk, where a jug of water was sitting, and drank greedily, getting more water on himself and the floor than in his mouth. He panted with exertion, and decided that he likely wouldn't be able to get to his door in this state, let alone find someone to help him at this time of night. So he decided to go back to bed, and thankfully this time, he drifted into the sweet embrace of sleep.

He woke up with the sun coming through his window, and a servant knocking on the door. "Come in." He groaned.

"Rough night sir?" The servant asked with a smile.

Leon's head was very foggy, and filled with cobwebs, so it took a minute to remember his awful night. Once he did, it took another minute to formulate a response. "Get Gaius."

"I have a hangover remedy from him here, if that's what you need."

"No. Something's wrong. Get Gaius." He was almost completely out of breath after pushing out those words. The servant realized that this was no simple hangover, and hurried out the door. While he was waiting, Leon caught his breath and stared at the ceiling.

He felt better than last night, he could open his eyes with some difficultly, but his head was pounding, and his limbs felt like lead.

He'd never admit it, but he was scared. Last night felt like a nightmare. He prayed that Gaius could cure this, if he never experienced the awfulness of last night again, it would be too soon.

A/N This story is inspired by an illness I have called POTS(postural orthastatic tachycardia syndrome). I'm trying to be accurate when describing the symptoms, but since some of the symptoms are brain fog and memory loss, I might make some mistakes. There is a whole slew of possible symptoms, not everyone gets the exact same symptoms, so don't be surprised if Leon doesn't get every possible symptom. This illness usually affects young women, but anyone can get it at any age. It's estimated that somewhere between 1-3 million Americans have it, and who know how many worldwide. I got it after a case of viral bronchitis, so that's how Leon got it, but you can get it from other things like after surgery, pregnancy, a car accident, and others, including get it and have no idea why. Thank you for reading, I hope you enjoy!