I've been trying to figure this song out on the mandolin, and it's just not working. I've tried using Em, C, and D, but from what I can tell in this YouTube video, he sings it in the key of F# minor, which doesn't make sense with those chords.

Here's the video:
Turning Away - Dougie MacLean with Kathy Mattea

Is the version you all are referring to in a different key?