The Essex Serpent is set in 1893, and the six-parter follows newly-widowed Cora Seaborne, who is finally freed from an abusive marriage when her husband dies. Keen to start afresh, Cora moves from London to the small Essex village of Aldwinter and becomes intrigued by a local superstition that a mythical creature known as the ‘Essex Serpent’ has returned to the area.
Cora explores the rumors of this mythical sea dragon, a kind of dinosaur that survived extinction. But she soon clashes with the local vicar, Will Ransome, who’s determined to lay superstition to rest in his rural parish, dealing with the frightening rumors as they begin to spread throughout the community.