When the tone and mood of a work of fiction are considered, it is important to be able to distinguish between them carefully. The tone of a piece of literature is defined as the manner in which a story is told and therefore relates to the author's intentions on how he or she chooses to relate the tale. If the tone is related to the author, the mood is related to the reader, as it can be defined as the mood as experienced by the reader as they read the tale. Often a tone can be very different from the mood, as in the case of a story where the tone is flippant or lighthearted deliberately to contrast with a serious or terrifying mood.
The tone of "The Fly in the Ointment" can be defined as serious and angry. This is relayed through the realisation of the son that his father is a man with "two faces," and this is a realisation that disturbs him:
There was the outer face like a soft warm and careless daub of innocent sealing-wax and inside it, as if thumbed there by a seal, was a much smaller one, babyish, shrewd, scared and hard.
The sight of his father's two faces repulses the son, and the anger that is expressed in their relationship is captured in the way that they speak to each other and the surfacing of barely concealed grudges and annoyances.
The mood, however, is one of overwhelming sadness, as the reader is left with an impression of a son who is desperately trying to reach out to his father and to show his love, but who is rebuffed at every turn. Even when the son reveals the money that he has, this causes his father's other face to emerge, killing any possibility of a rapprochement between them.