I'm doing a Silent Witness marathon on BBC iplayer. So far, the show has been at its best when focusing on 'familiar territory'. Any stories dealing with foreign locales or ethnic/religious minority groups are, for the most part, problematic. (One exception would be the superb 'Life Cruise' episode about the Holocaust, back in 2000). In general, though, portrayal of non-white, non-British/non-Western cultures and settings tends to be stereotypical, reductive and often 'white saviour' narratives.
The reasons for which a born-and-bred British person will end up joining the Taliban may be much more complex and nuanced than what this story suggests. Nikki's and Leo's interventions and speeches seem naive at best, patronising at most.
I do appreciate it when writers try to experiment or verge to unusual directions for a TV series but, so far, Silent Witness is at its best only when it 'works from home', as it were....