In the The Moving Finger Reverend Caleb Dane Calthorp works as a vicar in Lymstock with his wife Maud Dane Calthrop. Jerry Burton describes him as "a being more remote from everyday life" than anyone he had ever met. He is focused on his books, study, and knowledge of early church history.
In The Pale Horse he and his wife are now settled in the vicarage of Much Deeping in Devon. Like in the previous book he is deep in his studies and his contributions to conversations are usually limited to quoting Latin or Greek aphorisms. He doesn't play as big a role in the plot as does his wife in this book.
Mr and Mrs Calthrop are important crossover characters. Her presence in The Moving Finger puts them in the Miss Marple universe. Their presence in The Pale Horse puts them in the same universe as Rhoda Dawes, Hugh Despard and Ariadne Oliver, in other words, the Hercule Poirot universe.
In the ITV 2006 adaptation of the novel (Episode 2, Series of Agatha Christie's Marple), Rev Calthrop is played by Ken Russell.