Reading His Suspect to Sleep As "Endeavour" begins Sunday night on PBS's "Masterpiece Mystery!," we first glimpse the young Detective Constable Endeavour Morse singing in a choir. Those with the Morse bug, or the British mystery bug in general, will remember that the first episode of "Inspector Morse" back in 1987 began with the middle-aged detective inspector's rushing from a crime scene to a choir rehearsal. Mission accomplished. Having started last year with a single episode, the prequel series "Endeavour" is now starting fresh with a four-episode first season. Given another opportunity to wallow, tastefully, in nostalgia for its predecessor, the new show doesn't miss a beat. A substantial audience - more than seven million viewers in Britain - is happy with that, and "Endeavour" has already been renewed for a second season. Other viewers - those who watch mysteries for the mystery - may lose patience as the episode's overly complicated plot, involving a dead secretary, a doctor murdered in a public restroom, a series of post office robberies and a love child, is resolved haphazardly and implausibly. So if you're looking for a solid British detective yarn, check out "DCI Banks" (Season 1 is in reruns on PBS stations, including Channel 13 in New York) or wait for "Case Histories" to return. "Endeavour" offers a different and not negligible set of pleasures: it's like a table perfectly set for afternoon tea, cress sandwiches here, clotted cream there. Sit for 90 minutes, have a cup of orange pekoe and feel satisfied. Having just joined the Oxford police, Morse immediately makes enemies when the astute inspector Fred Thursday (Roger Allam) chooses him as bagman, a position that should have gone to a sergeant. The references to bagman, meaning chief assistant, are part of a self-conscious effort to use language to remind us that the action is set in the early 1960s: A constable discovers a French letter (condom), and Morse remarks on a vicar's interest in cruciverbalism (crossword puzzles). The tastes for puzzles, opera, poetry and flashy cars that the novelist Colin Dexter originally gave Morse have become an orthodoxy after nearly 40 years of books and television shows, and they're reverently invoked here. Morse reads a troubled suspect to sleep with Tennyson's poem "Lady of Shalott," best known for giving Agatha Christie the title for "The Mirror Crack'd." A larcenous character is referred to as la gazza ladra, Rossini's thieving magpie. Morse's red Jaguar Mark 2 is in the future, but he gets to drive the police force's black Mark 1"s. The lead actors do good work, even though their job, to some extent, is to make themselves part of the period décor. Shaun Evans makes Morse appealing, despite his twitchy pride, and Sean Rigby brings a vulpine grace to Constable Strange, Morse's current subordinate and future boss. Best is Mr. Allam (the original Javert in the London production of "Les Misérables") as the heroically reserved Thursday, alternately flashing his affection for, and exasperation with, Morse. In the course of Sunday's episode Morse develops one of his patented hopeless crushes on a suspect, and it gets him busted down from bagman to general duty. You're a good detective but a poor policeman, Thursday tells him, and something similar could be said of "Endeavour": it's a poor mystery, but it's not a bad meal. Masterpiece Mystery! Endeavour, Series I On PBS stations on Sunday night (check local listings). Produced by Mammoth Screen Ltd. for ITV and Masterpiece. Written by Russell Lewis; Michele Buck and Damien Timmer, executive producers; Dan McCulloch, producer. WITH: Shaun Evans (Detective Constable Endeavour Morse), Roger Allam (Detective Inspector Fred Thursday), Sean Rigby (Police Constable Jim Strange), Anton Lesser (Police Chief Superintendent Bright) and Abigail Thaw (Dorothea Frazil).