Arsenic and Old Lace Beginning with acts such as Abbott and Costello, and episodes of "I Love Lucy," humor is often the result of a misunderstanding. In the movie, "Arsenic and Old Lace," the plot combines murder and insanity. "Arsenic and Old Lace," seemingly outlines a mystery or drama, however with the addition of misunderstanding, it becomes a comedy. The humor is drawn from the characters' relationships with one another as well as the characters themselves, being misunderstood. The movie centers on two sisters, Abby and Martha, and their nephew Mortimer. The misunderstanding lies between the sisters and the townspeople. Abby and Martha are known as sweet,