I am enjoying this second series more than the first one, maybe because the characters are sort of well established and developing nicely. I am also glad that the sanctimonious Bishop character is out of the way, and Nolan is paired off with different characters with a different range of personalities.
Also, this episode presented a major ethical dilemma, concerning the father's responsibilities in sending his son to rehab with all the consequences. It was definitely tragic and a tad unbelievable, but handled in a decent way. Life sometimes offers no good choices but only "less bad" ones.
The chemistry between Chen and Bradford is working very well, I see them as a couple, but probably it won't happen. The only negative part was Nolan's meeting with his ex, who's obviously extremely attractive and dangling like an irresistible temptation... although I think Nolan's current relationship does not really work, both because the actors have zero chemistry and in the fiction their characters don't work together: she's too smug and he's too soft.