In Dr.Thorne, the third of the six Barchester novels, Trollope moves outside the cathedral close to follow the fortunes of Dr Thorne, an upright and principled country doctor, and his niece Mary. She falls in love with Frank Gresham, heir to the heavily mortgaged Greshambury estate, but he is constrained in his choices by the need to marry well so that he can restore the family fortunes.