I saw this particular episode some two to three years ago. The performance by Emily Browning was a revelation! It is rare that I remember any actor's or actress's name, but Emily's was burned into my brain by her unbelievably mature and insightful portrayal. She shone, and frankly ran rings around our (sadly well outclassed) star of the show.
I was pleased, and not at all surprised, when I heard last year she'd won the role in Lemony Snickett. I'm not surprised - as I just learned - her interests include literature, philosophy and psychology (imdb bio). I hope she continues to bring her special insights to her acting, and that she will be seen, internationally, for a long time to come.
The world will certainly be the richer for it.
Christie (Browning) has been charged with murder of a school friend, and Halifax (Rebecca Gibney) has to assess whether she is fit to stand trial. On the way to her decision she is confronted with a very intelligent, and very confused girl, who already seems to know all the answers, and is also hiding a terrible secret. As the layers are stripped away from Christie, Halifax discovers the terrible secret, and solves a long lost murder mystery.