Having read the other reviews here I think that most posters have got it right - it was painful to watch. But I have to disagree with awarding this more than an 8.
Where was the drama? What happened to the action? The episode does start well and builds up a fair level of intrigue but it dovetails all to quickly. The H5N1 virus storyline was good, but there where very little scenes to show us the impact of such a discovery, other than adding some much needed urgency. The use of 'illegals' could have been much better and though logical just didnt add much to the 50 odd minutes.
The subplot of Amita and Charlies relationship trouble was limited and just didnt fire my imagination. It did provide a nice little angle as to what the future brings for Charlie and how his character may become affected in the next series. However, I just didnt feel any real connection with their dilemma, perhaps because Ive yet to feel their relationship to be what the writers think it to be because lets face it they haven't really explored their feelings in previous episodes.
The casebreaking clue (tattoo) has been done before so there was little new added here and the overall chase to find the suspects who dumped the sick girl and left the others for dead just didnt roll as urgently as previous storylines. There was a noticeable lack of maths which as Ive seen in previous episodes seemings to be growing. The writers are just dumbing down the inclusion of what is the a really interesting aspect of this show.
Howewever, its not all bad - the finale comes round realistically enough and ends in a satisfactory conclusion, even it its nothing spectacular.
Not a good episode and if you miss it then I wouldnt worry to much, as you can just go over the very good recap added here.