One of the novel’s central themes is the battle between faith and reason. This is best exemplified by the townspeople’s belief in the Essex Serpent. The mysterious creature, which can trace its history back 200 years, is blamed for the disappearance of children, adults, and animals. It is also credited with bringing a malign influence to the village of Aldwinter and casts a dark pall over the village that seems impossible to shake. However, few people can credibly claim to have seen the monster. Its existence and its nature become the primary battlegrounds for the conflict between faith and reason.

The way this conflict manifests in the text is unexpected. Here, Cora represents faith, as she wields the powers of natural science and the work of some of the era’s most important scientists in order to justify the existence of the Serpent. She cites living fossils discovered elsewhere, as well as the work of many of her forebears in the scientific world, in the belief that the Serpent could be real and could be lurking beneath the Blackwater. This creates an interesting internal juxtaposition. In the text, the sciences represent faith.