Who is the protagonist in play arsenic and old lace?

The play Arsenic and Old Lace has multiple main characters, but two of the most important are the Brewster sisters, Abby and Martha. Abby and Martha are the central figures in the play, and their actions drive the plot. They are elderly sisters who live together in a Victorian mansion in Brooklyn, New York. They are portrayed as being sweet and innocent, but they also have a dark secret: they have killed multiple elderly men by poisoning them with arsenic-laced elderberry wine. The Brewster sisters are the protagonists of the play, as the story revolves around their lives, their relationships, and their actions. They are the characters that the audience empathizes with and follows throughout the play.