Set in the Victorian era, in the year 1893, it tells the tale of Cora Seaborne, a woman relishing her recent freedom from an abusive husband — she moves from London to a small village in Essex and becomes intrigued by the idea that it might be haunted by a mythological sea serpent.

After being widowed when her wealthy, abusive husband dies of throat cancer, Cora Seaborne decides to ignore the trappings of her London society life and take up amateur palaeontology.

While on holiday in Colchester with her son, Francis, and her companion, Martha, Cora is intrigued by a ruin caused by an earthquake which was rumoured to have awakened the Essex Serpent, a mythical sea dragon.

The Ambroses tell her of friends of theirs, the Reverend William Ransome and his family, who live in the small village of Aldwinter where a serpent is carved in one of the pews of the church.

After a visit to the local school results in the schoolchildren falling into fits, Cora seeks an explanation by inviting her friend, Dr Luke Garnett, from London to examine them.

She ignores Will and writes an angry reply to Luke, only discovering later that her letter reached him the same day that a knife attack maimed him permanently and ended his medical career.

Living alone, since her companion Martha has fallen in love and her son is in boarding school, Cora is happy in her solitude but continues to write to Will, urging him to reunite with her one day.

Barnard and Symon are producing with Jamie Laurenson, Hakan Kousetta, Patrick Walters, Iain Canning, Emile Sherman and Andrea Cornwell via See-Saw Films for Apple.