Originally published in 1948, The Clue to the Brontës was written in part as response to a previous biography of Charlotte Brontë by Mrs Gaskell. The author argues that Gaskell's biography gets it all wrong. Harrison draws connections between Patrick Brontë and John Wesley. She finds Gaskell paid too much attention to gossip and did not verify her facts.

The influence of John Wesley and the revival of evangelical religion is seen as a force in the Romantic Movement's impact on the English novel. The same influence is here seen to be at work in the writings of the Brontës, including those of their father Patrick.