Thinking of this reminded me of a Sherlock Holmes story which I haven't read in years: The Adventure of the Dancing Men. In it, Holmes is visited by a man named Hilton Cubitt who is worried about mysterious coded letters that his wife has been receiving. He explains that, before they married, his wife- an American- had asked him to never ask her about her past. Without going into detail, she told him that, while she herself had never done anything wrong, she had "very disagreeable associations" in her past life in the States. He agreed and they married, and had been very happy together until these notes started arriving, mailed from the United States. His wife, Elsie, has become deathly afraid, but refuses to tell him the meaning of the notes. Cubitt has brought all of the notes to Holmes to examine and leaves them with him, returning to his home in Norfolk.
Holmes examines the notes which consist of series of little dancing men in various positions:
Slaney shows up thinking that the note was written by Elsie, not knowing that she has been wounded. He is captured and, knowing that the jig is up, confesses. He explains that Elsie is the daughter of the crime boss he works for in Chicago. He and Elsie were engaged to be married, but she wanted nothing to do with a life of crime and ran away, fleeing to Britain to start a new life. Slaney eventually tracked her down and came to England to get her back, sending her the menacing messages in the code only she and he would understand. And Holmes, of course. Slaney showed up at the Cubitt's house and was talking to a frightened Elsie through a window when Hilton saw him and took a shot at him. Slaney returned fire, killing Cubitt, and fled the scene; Elsie, apparently blaming herself for her husband's death, shot herself. Slaney is tried for murder and sentenced to hang but his sentence is commuted to penal servitude because Cubitt fired the first shot. Elsie recovers from her self-inflicted wound and spends the rest of her life using the money she inherits from her husband to help the poor.