Undercover Undiscovered

The BBC Sunday night thriller concluded last night, but only in the sense that the last episode occurred leaving me, for one, very much in the dark about who did what and, more importantly, why (not helped by lead characters having key conversations in plain sight but out of earshot of the hapless viewer); were the loose ends just sloppy writing or, more likely, deliberate ploys to pave the way for Undercover 2, which would be an undercover too far for me.