Orlando Falkland's slipping into the ha-ha issues in the novel's plot and its principal moral dilemmas.
He has fallen into the ha-ha after being encouraged to leap over it by Sir Edward Audley, whose sister is Dolly's friend:
Inger Sigrun Brodey has read the ha-ha in Mansfield Park in terms of an ambivalence regarding authority: the ha-ha acts, on the one hand, as a form of authority that relies on external constraint--"restriction that is imposed externally," against which the young inhabitants of Mansfield rebel--but also more desirably in "the authority that is felt in more subtle ways, in the form of an internal conscience or sense of delicacy" (93), which Fanny possesses.
Orlando has indeed stepped beyond those bounds, trying to reach beyond the ha-ha that figures domestic restraint.
For Maria and Henry, however, the ha-ha is a precipice that suggests their fall and ultimate exclusion; Maria's transgression of legitimate familial constructions results in her exile outside of Mansfield "in another country--remote and private" (538).