I Used to Know

When Arthur accidentally eats rat poison, Merlin has to save him with magic. Arthur only half remembers the experience, however soon Morgana hears about Merlin's supposed magic. With Morgana trying to get rid of Merlin, and Arthur now unsure about where Merlin's loyalties lay, the warlock is in very deep trouble. Will he be able to prove himself? eventual hurt/sad!Merlin No Slash