They are forever shocked to be visited in their country manses by inspectors and constables, perpetually fussing over tea in drawing rooms full of quite guilty-looking suspects. It's time for a string of old-fashioned Agatha Christie murder mysteries, but with a cutting-edge host. The black, white and blood-red graphics of PBS's 'Masterpiece Mystery' are perfectly matched to the black suit, white shirt and blood-red tie of Scottish actor Alan Cumming, our host this season, luring us into six nights of Christie murders. Beginning Sunday night and continuing for six Sundays (through July 26), 'Six by Agatha' on PBS brings two Hercule Poirot and four Miss Marple mysteries to the small screen. The first is 'Poirot: Cat Among the Pigeons.' David Suchet is now in his 20th year as Poirot, his signature role, while Julia McKenzie ('Cranford') takes on the iconic Miss Marple for the first time. She follows in the clunky brown oxford shoes of Margaret Rutherford, Angela Lansbury, Joan Hickson and Geraldine McEwan. Suchet's spats-and-pince-nez-wearing Poirot is a rather comical caricature by now, while McKenzie's Marple is fresh as the keen-eyed, gray-haired, knitting and always listening sleuth. Between the two of them (Christie fans know the characters never met in all of the author's works, although they often worked the same beat), they run across lots of bodies. Lots of impressive guest stars too. Joan Collins ('Dynasty') plays Marple's old school chum in 'They Do It With Mirrors.' Rupert Graves ('Forsyte Saga') is an effervescent prodigal son returned from Africa in 'A Pocket Full of Rye.' Matthew MacFadyen ('Little Dorrit') plays a police inspector, and Prunella Scales ('Fawlty Towers') portrays a bitter widow, also in 'Rye.' Jemma Redgrave ('Bramwell') and David Haig ('My Boy Jack') appear in 'Murder is Easy,' and Zoe Wanamaker ('David Copperfield') is an eccentric mystery writer who follows Poirot. Each whodunit is a Devonshire-cream-rich 90 minutes. ------ You've got to hand it to the Palins: No matter what you think of the Alaska governor and her family, they did drag an embarrassing topic into the national conversation. And let's not even bring David Letterman and his apologies into the discussion. The whole mess (boring by now and useful mainly to political smear campaigns) has shed light on a previously dark corner of American life. Now, ABC News cashes in, with 'Primetime: Family Secrets,' a look at hidden family dilemmas like child abuse and teen pregnancy, on Tuesday. ------ If you have an old computer monitor or analog TV sitting in the garage, you're not alone. In its season finale, 'Frontline/World' follows the 'dirty secret of the digital age,' the hundreds of millions of pounds of electronic waste that accumulates annually around the world. 'Digital Dumping Ground,' Tuesday on PBS, tracks the 'e-waste' to Ghana and China, where it's scavenged for precious metals. A team of graduate journalism students working with producer-correspondent Peter Klein follows the used hardware and explores potential threats to privacy, as criminal gangs glean data from America's old computers and cell phones. (Joanne Ostrow, TV critic for The Denver Post, can be contacted at jostrowdenverpost.com.) 