I'm with Bethany Cox (TheLittleSongbird) on this one. It has everything (and I can hardly ever say that, so giving something a 10 rating is extremely unusual for me). It has suspense, shock, family feelings within and around the team as well as within a victim family. Unusually we sense family feelings between the team and the victims, and with the perpetrator, who also provides unexpected pathos.
I think that all concerned deserve commendation for the way that A. J. Cook's pregnancy is blended in, rather than being disguised as often happens in other shows. The other particular high point for me is Jane Lynch's performance, emphasising how capable she is when dealing with serious drama, as well as having an immense comedic talent. I can't help wondering about the result of pairing up Jane Lynch and Olivia Colman, in a serious drama and in a comedy. I suspect both would be hugely successful!