Summary review:

Plot as good as before (suddenly everyone's immortal).

Possibly moving from an episodic layout (each week a new story) to a season-length plot? Not sure about that.

Seem to be moving from slightly quirky Cardiff setting to Washington DC -- might be turning into yet another Washington FBI/CIA drama. A cynical move to get a bigger US audience? Might be losing it's edge on originality.

Will still watch next week.