There are three characters in the story: the boy, his father, and the doctor.
The boy (Shatz) is old enough to understand that you can’t live with a temperature over 44 degrees, but young enough to confuse Celsius and Fahrenheit.
The boy’s father (and presumably his mother) notice that he is sick.
He was shivering, his face was white, and he walked slowly as though it ached to move.
The doctor tells the boy’s father that the fever is due to influenza, and gives him medicine. The doctor says it is ok as long as the fever does not go about 104 degrees, but the boy is convinced that he is dying because he heard in France that you can’t live with a temperature over 44 degrees. The father feels sorry for him, and explains that it is just a different thermometer.
Although the boy has a good relationship with his father and his father is sympathetic, apprarently they do not have a close enough relationship that the father makes sure that the boy is not worried before he goes out hunting.