Duncan’s fate in “Saltburn” might get people talking more than the infamous bathtub scene. The movie almost seems to forget him, even if the screenplay suggests Oliver may try to kill him at some point. But getting rid of Duncan likely won’t be as easy as the Cattons. To understand this, one must consider the symbolism the butler plays within “Saltburn.” Consider this rumination from Redditor u/constnt: “Duncan is the spiritual manifestation of the House. Of Saltburn [itself]. And Saltburn is more than a house, but a place in society. The highest tier in the social hierarchy.”
Evidence of Duncan representing Saltburn itself is seen in the film. For example, there’s the breakfast scene where Oliver doesn’t know the etiquette of getting his own breakfast sans the eggs, which are prepared for him. Oliver doesn’t belong there, and even though Duncan isn’t rich like the Cattons, he still adheres to the social etiquette exemplified by the highest echelons of society. Oliver may own the house by the end, but he doesn’t belong in this specific social stratification.
Oliver uses his perceived “poor” upbringing to get Felix and the Cattons to like him. They’re taken in by his sob story. One surmises Duncan was never fooled and always assumed Oliver planned on manipulating the Cattons. In the event Oliver tries to manipulate Duncan, he likely wouldn’t be successful. The ending of “Saltburn” may make it seem as though Oliver wins in the end, but it could be temporary. Oliver may not control Saltburn for long, and when he goes, Duncan will remain. Oliver should dance while he can because Duncan’s lying in wait.