In his lifetime, Lovecraft grappled with the fear of inheriting unfavorable genetic traits and predispositions. Lovecraft explores this fear throughout many of his works, and one of the major themes of “The Rats in the Walls” is the ominous connection between Delapore’s identity and his family history. For much of his life, Delapore knew little about where his family came from. His family history was written down and kept in an envelope, which Delapore says was tradition among American families during the Civil War. When Union soldiers attacked the Delapore plantation and set it on fire, the envelope burned. However, Delapore felt no great loss in the burning of his family record:

Neither my father nor I ever knew what our hereditary envelope had contained, and as I merged into the greyness of Massachusetts business life I lost all interest in the mysteries which evidently lurked far back in my family tree (Paragraph 4).

Although Delapore is content in his ignorance, the word “lurked” foreshadows Delapore’s unsettling discovery of his heritage. Delapore becomes more interested in learning about his family’s history after his son dies. Alone and with no other living family, Delapore seizes the opportunity to feel purpose and meaning in his life.