You'd think that after 7 seasons and 7 years of A Touch of Frost the quality would diminish as ideas dry up and/or the cast lose motivation. Turns out, quite the contrary.
The series is actually getting BETTER. The producers have figured out that the ideal format for Frost is not several independent 90-minute episodes in a season but one 150 or so minute episode split into two parts. You have more time for plot and character development and can mesh several concurrent mysteries into one episode.
Season 7 was the first time this was tried and it was great. Season 8 is even better and is absolutely brilliant. There's a few mysteries, some of which get wrapped up pretty quickly and one, the centrepiece, that goes the distance. With any other show there'd be a connection between the different cases but not with Frost, showing that policework isn't about tackling one crime at a time but tackling them simultaneously.
Add in a great human aspect as Frost is teamed with a Sergeant who is a war hero but who also has many issues and an emotional sub-plot involving Frost's private life and this is about as complete and as perfect an episode of Frost (or almost any detective drama) you'll get.