The programme is set during, and after, 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, very sagacious and scrupulously honest, yet 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.
Each episode runs for about 95 to 100 minutes, filling a two-hour slot on ITV when commercials are included. To fit PBS's 90-minute time-slot in the United States, episodes, particularly in Series 1–3, were edited by several minutes each.
In a newspaper article and in his interview that accompanies the first series DVD set Anthony Horowitz was asked why he named the main character Christopher Foyle. He explained that he was seeking a name that evoked the early 1940s and thought of Foyle's Bookshop in London's Charing Cross Road, once known for its archaic practices and its owner Christina Foyle. Christopher was the nearest male name to Christina, but from 1999 following the death of Christina Foyle, control passed to her nephew Christopher Foyle, who was given a small walk-on cameo part in the episode "Bad Blood".
Series 7 commenced filming in February 2009 and premiered on UK television 11 April 2010.