Foyle's War combines history and mystery in a mix that is entertaining and educational. I highly recommend it, especially since excellent movies have become scarce. We record it on the DVR from PBS and watch it instead of going out to a movie. I wish they could produce more than four episodes per year!
Here's an overview from Wikipedia:
The programme is set during the Second World War in Hastings, England, where Detective Chief Superintendent Christopher Foyle (Michael Kitchen) attempts to catch criminals who are taking advantage of the confusion the war has created. He is assisted by his driver Samantha "Sam" Stewart (Honeysuckle Weeks) and Detective Sergeant Paul Milner (Anthony Howell).
Foyle, a widower, is quiet, methodical and very observant and is frequently underestimated by his foes. Many of his cases concern profiteering, the black market and murder. Foyle often comes up against high-ranking officials in the British military or intelligence services who would prefer that he mind his own business but he is tenacious in seeking justice.
The stories are largely self-contained. There are some running strands, mainly involving the career of Foyle's son Andrew (played by Julian Ovenden), a fighter pilot in the Royal Air Force, or Foyle's continuing relationships with cameo characters.
Here's the description of the latest series, shown in the US in the Mystery! slot on PBS.