Everything you need to understand or teach The Old Contemptibles by Martha Grimes.
While many other detective novelists employ the "murder will out" theme, Grimes's theme instead is "murder must out." Unsolved crimes from the past in this novel have effects that carry over into the next generation and cause even more crimes. The apparent suicide of Jane Holdsworth at the beginning of the novel seems unmotivated by the events of her life immediately preceding her death; only through exploring her past and that of her late husband's family can Jury make sense of her death. The shooting of the murderer by family members of her victims is a primitive, personal sort of justice, "rough justice" as one of the characters calls it. The crimes are viewed as being against the family rather than against society.