In the play "Arsenic and Old Lace," the aunts, Martha and Abby Brewster, do not fit the typical profile of successful serial killers. They may appear innocent and kind-hearted, but their actions of poisoning lonely old men reveal their dark secret. Their probable next victims are elderly, single men who they believe to be lonely and in need of "mercy." It is important to note that this is a fictional play and not a real-life portrayal of serial killers.