Wonderful story. I think you've captured Merlin's depression and Arthur's helplessness beautifully. I'd really love for the show to take Merlin to such a dark place, because it feels so real. Merlin has such a big heart it's difficult to imagine him not being profoundly altered by the events of late S2 and Colin is more than up to the challenge. If your muse strikes, I'd love to see where you go with this.

Best of luck on your exams! It's hard to believe you're still in high school, your writing is so polished and shows a level of emotional maturity not often found in younger writers. (But, then, as I know from experience, dealing with depression at a young age can make you grow up pretty fast.) Anyway, you're very talented and I look forward to reading more from you!