Season of Darkness by Maureen Jennings

Set during the early days of WW2 in northern England, Tom Tyler, the sole detective in his area, finds himself challenged to find the culprit that killed a young lady as she bicycled to work. Things become complicated as Tom deals with a broken marriage, an unhappy daughter and a son who suffers from PTSD from the battle of Dunkirk. Now a former lover arrives in town to really cloud the waters. Is the culprit a local or a Nazi spy?

This is a cozy mystery that will appeal to fans of Louise Penny or Agatha Christie. This is the first of four books in the series.