Disclaimer: Sadly I don't own Merlin, BBC does.
It was an unevnful day. Camelot just smoothly adapted new routine. Gossip surrounding royal wedding was dying down. The repairs of city were over and everything just seemed to be getting better, so Gaius was not surprised to see his ward return in late afternoon instead of late in evening, spotting big grin. Nor when, his good spirit wasn't broken by being ordered to go gather some herbs.
No, the day was quite peaceful and Merlin looked quite pleased with the world, when he returned with lots of herbs to find Gaius just about to serve dinner. He had put the herbs in their respective places and was just about to head over to the table, when he suddenly dropped to this knees clutching his head.
Gaius was shocked at his ward state and tried to find out what was wrong, but Merlin only mumbled something about it being too dark, which for one terryfying second brought Gaius back to the time he was poisoned, but he put himself together. Whatever was happening to Merlin seemed like panic attack combined with severe headache, so he poured down his throat a strong calming and then sleeping drought. And managed to get him in bed before they kicked in fully.
He watched him turn and toss in uneasy sleep as he mumbled about how "walls are closing on me... can't move... can't breath... " He hold his hand and rocked his brain for something that could help as his heart sunk with worry. There was only one explanation for Merlin's current state - sorcery. It did not take a genius, to realise that whatever was happening wasn't good and Gaius tried hard to not think about what sort of trouble had his charge landed in now. He should have known by now, that it won't work.
Merlin's POV - at the same time
Merlin was happy. Gaius recovered from this latest Morgana's siege. You would not realise, that the city was recently under a siege, looking at Camelot now. Gwen was back and finally married to his royal pratness and to sweeten it, he got dismissed early. His good mood could not be challenged by being asked to pick herbs for Gaius, because quite frankly, he enjoyed doing so.
He got to be alone in a forest, which reminded him of being home, not to mention allowed him to use his magic. It was peaceful and nice, especially on such sunny autumn day, as was today. He entertained the idea of calling Killgaraah and Aithusa, but he did not wish to risk them being seen, after all there were rumours about what happened to mercenaries chasing them to and from Ealdor.
He couldn't help, but smile, when he returned home to find Gaius preparing dinner. He carefully put herbs in their respective places and turned around, when it happened. He suddenly felt so afraid, so trapped and helpless, it was so dark and he hurt all over. He heard somebody talking. He vaguely noticed someone holding him, pouring something - Gaius's potions going by taste - down his throat. The person, that must have been Gaius dragged him to his bed, but at the same time he felt trapped and unable to move. No he wasn't trapped but someone els was, crying for his help, in the same manner as the druid boy did, only without words, but who?
Merlin dreamt, but it was all to real. He was trapped, he was curled and there was not enough space for him to straighten. His body was protesting to this. His legs were tingling, his muscles cramping. He was in dark. Someone was caressing his cheek, holding him, trying to sooth him. He knew that voice, but it couldn't be. And yet it was. It was Morgana. She spoke with kindness and warmth, he did not know, she could still possess, but her voice trembled with fear. Fear of light. Because with light come pain.