Television preview RECOMMENDED VIEWING THIS WEEKEND

"The mystery novel must... consist of the plau-sible actions of plausible people in plausible circumstances" - Raymond Chandler.

The Prime Suspect films - for all their socio-political content - are primarily mystery novels, adapted and updated for 1990s television. The same rules apply. Chandler went on to add, in case you're wondering just how plausible a character like Philip Marlowe is, that "plausibility is a matter of style".

The style of the first few Prime Suspect films was scrupulously realistic - Helen Mirren leading the way with her dressed-down portrayal of DS Tennison. The idea was that by showing the police as they are, a few hard political realities (sexism, racism and homophobia in the force, for example) could be tackled along with a cracking good story. Or rather the story was pitched in such a way as to uproot these issues as it went along.

Prime Suspect 5 (Sun ITV) begins promisingly enough, with Tennison transferred from the Met to Manchester, where her first big case involves a drugs turf war in the city's grim housing projects. The trouble starts when we meet the central villain, a ferrety gang leader called "The Street", a greasy-haired Machiavelli with a penchant for feeding his victims to his Rottweilers. I may be wrong, and super-villains like "The Street" do exist, but he seemed to me to be a fictional construct, and one that unbalances Prime Suspect's otherwise present-and-correct traditional strengths. It's a major misgiving, but there's still plenty here to keep you watching.

No misgivings about Loving (Sat BBC2), the most enjoyable Screen Two I've seen in a long while. It's a careful and skilful adaptation of the now almost forgotten novelist Henry Green's satire about a group of domestic servants in an Anglo-Irish stately home in 1941. Ireland, of course, was neutral at the time.

Green's ear for dialogue - and the tortured working-class speech patterns of the time - is beautifully reproduced by Maggie Wadey. Mark Rylance is superb as the cunning but essentially weak butler, and the seriously sexy Georgina Cates captivates as the housemaid unpredictably wavering between knowingness and childish innocence. A delight.

The pick of tonight's Fame Factor is Didn't You Used to be Satan? (Sat C4), which catches up with the now grown-up Linda Blair, erstwhile child star of The Exorcist. A hotly disputed cocaine bust when she was 18 ended Blair's lucrative mainstream career, restricting her to B-movie horror films ever since.

Everyman (Sun BBC1) explores how, when faced in 1945 with the aftermath of the Nazi genocide, some Jews decided not just to get mad, but also to get even. Selected assassinations of SS officers ensued, and one group decided to poison the water supplies of German cities, starting with Hamburg and Nuremberg. They infiltrated the requisite pumping stations, and this week's film tells how it didn't in the end happen.

The Natural World (Sun BBC2) spreads the little- known fact that penguins are not only beautiful (when shot underwater, at least), but also exist happily in tropical climes as well as on those more familiar ice packs. If you can watch the footage here of a penguin waddling around a leafy forest glade without a smile on your face, then you're probably the sort of person who could never see the funny side of Monty Python.