Name one main theme introduced by the novel's epigraph in The Death of Mrs. Westaway.

Ruth Ware includes an epigraph at the beginning of the novel The Death of Mrs. Westaway that evokes the feeling of a nursery rhyme. At first, the elements named for each number seem relatively innocuous, with one standing "for sorrow," while two stands "for joy" (1). By the end of the rhyme, however, the theme of secrecy arises, casting a slightly darker mood over the epigraph and hinting at the theme of secrecy being a main component of the narrative to come. The final two lines of the epigraph state, "Seven for a secret/Never to be told" (1).