I don't know why, but everyone who comments on this show feels a need to outline each of the characters, with a short "bio" and some personal remarks.
What's curious about this is that the show's uniqueness comes from Gabriel Byrne's performance, and the subtle variations in his dealing with each patient. Their problems and dilemmas are somewhat secondary to his attempts to address them, which, ironically, is only possible because the other actors are absolutely brilliant.
All that said, Sophie is fascinating, not only from the character/plot/script standpoint, but from the unbelievable performance by Mia Wasikowska. She was the only one in the show I had never heard of or seen anywhere else, and for this kind of incredible performance to spring out of nowhere, it's clear she's sold her soul to the devil, and truly gotten her money's worth. Looking forward to seeing her in everything else she does.