"You don't know anything about that!" Merlin would not be accused of leaving his mother to die. Arthur had no right. The sorcerer looked torn between being angry and guilty, his thoughts drifting to the time his mother had suffered, and seeing Gaius dead. He hadn't even gotten the chance to see if his mother was okay before being pulled here.
"She was never supposed to be involved! I traded my life for yours, but Nimueh --" He threw up his hands in frustration, pacing slightly, fear creeping in that perhaps it hadn't worked at all. That he'd saved Gaius, but his mother had still been left suffering. Now he was trapped here, and if that was true he'd be to late to help her. "She twisted it, and then she tried to take Gaius, and I -- I killed her." He'd killed before, and tried not to let it get to him because it had to be done, he had to save Arthur, but it still -- It still made him a murderer, didn't it?
"I did - I hoped you would. I just," He faltered. "I couldn't. It was too much. Too much at once."