Colonialism
The story is set on a Polynesian island colonized by the British. Mr. Walker is a representative of the colonialism and the colonial state of mind, the belief of superiority. Not entirely a negative character, he portrays the thought of righteousness and justification of actions for the greater goods. He sees the natives as less than himself, sees himself as the authoritative figure that only means them well, even when mistreating them.
Racism
Colonialism and racism, needless to say, are terms that go hand in hand. Therefore, there is the theme of racism shown in the story, from the overall tone when speaking about the natives, through to the more intricate ridicule of tradition. Walker decides to take advantage of the native’s tradition of hospitality to trick them, lead them into a desperate situation, making them dependent on him. Racism is also shown in the caricatured character of Walker's Chinese servant.
Guilt
Mackintosh decides to turn a blind eye and let the natives have their revenge on Walker. He is plagued by guilt, and tries to warn Walker as well as he can. In his final conversation with Walker, he realizes that Walker is not the villain, but the system that groomed and appointed him to this position is, and decides to not go down the same path. From the very start, it is clear that Mackintosh is a more sensitive and sensible person than Walker, and having that in mind, the grim ending isn't that surprising.
