The plot turns on the forced stay of two married couples on a Pacific island called Pago Pago, due to the impossibility of continuing a ship voyage because of the threat of an outbreak of disease. One of them, Mr. and Mrs. Davidson, are missionaries in charge of evangelising the natives on an island and spreading the word of God to them. They share this forced landing with another couple, Mr. and Mrs. Macphail. This situation, already unstable in itself because of the circumstances, is further disrupted through the entrance in scene of Miss Thompson, a libertine woman who boasts of this attribute.
Driven by his missionary zeal, Mr. Davidson has no intention of letting this matter pass without more ado and immediately sets about to guide the stray sheep back to the fold. The underlying issue is not the missionary's good intentions, who certainly puts great determination for his task, but rather the misguided approach he takes in carrying out the responsibility every Christian has to help his neighbour. To contribute to another person's good means that we carry it out taking into account that we all are exposed to sin and that what distinguishes us from one another is the way we approach it, become aware of it, and struggle to avoid it (if we will).
Mr. Davidson forgets that he, too, is subject and target of sin, even though he is a missionary. For to know the life of Jesus (which he does know well and in detail) does not exempt him from being tempted; on the contrary, acting while blinded by the Truth, yet failing to let ourselves be guided by It, leads ourselves to do what we do through our own means and for ourself rather than through Him and for Him.
Here lies the error of such a Christian as this who is clearly embodied in this character. Naturally, this has consequences, since relying solely on our own fragile strength leaves the outcome subject to the arbitrariness of our desires. A pleasant and well-focused read that should not serve to point to the character as an example of what should not be done, but rather to question oneself about how far one would go and how one would act in pursuing the same goal.