A nice old-fashion episode, like the likes that were the norm in the first few seasons of this series, since here there is one strictly defined central story arc and any other scenes are minor and not very related with the plot line. The whodunit element is very good developed and is one of the few times that... the responsible party completely escaped my attention.
On top of that I will also say that the conclusion of the particular episode is satisfying, but I would like to see some other plotlines from the last season concluded. I don't mind occasionally to have stories that continue in two episodes, but too many of them will make this a soap opera. I am more of a fan of the traditional one story at the time, format.