"Promised Land" opens with Morse and Sgt. Lewis being ordered to New South Wales, Australia to seek evidence from a snitch from a prior case that was subsequently hidden "Down Under" with his family in a witness protection effort. The witness has "gone walkabout" by the time they arrive, however, and much of the episode is consumed by Morse and Lewis seeking him. They also interact with the witness' family and several of the locals, and try to track down another individual from England that appears to be seeking the same witness for more sinister purposes
The episode is unusual in that it takes Morse and Lewis out of their usual Oxford environs (like the following season's "The Death of the Self", set in Italy). On the whole, the case includes fewer twists and turns than many in the series, but that is counterbalanced in some respects by a more personal interaction between Morse and Lewis and by a few moments of atypical introspection on Morse's part about his police work (generally, his limited self-reflection has been built around his lack of lasting relationships).
The setting change also provides an opportunity for a much different backdrop to the case than the usual lineup of masters, dons, inellectuals and patrons. There are references to Australia's progressive independence from England and English culture, and to the Brits' view of the Aussies and vice versa, woven into the storyline for color. The episode was actually shot in Australia, and includes a scene of Morse, the avid opera fan, ascending the steps to the Sydney Opera House, and several shots of the sweeping Australian countryside, very different from most episodes' cinematography.
On the whole, it is not among the better Inspector Morse episodes for its mystery, but is very good from a character revelation standpoint and for its variety from the usual.