Clearly the theme of race is all-important in this excellent short story, as it is the importance placed on race and the colour of skin that leads Armand to turn against his wife and child, resulting in their deaths. By far the most important symbol in this story is therefore the son that Desiree bears Armand, and the way in which it has such a profoundly negative impact on their marriage. This symbol is actually interpreted for us by Armand himself, revealing its importance to the narrative as a whole. When Desiree one day truly sees the darkness of their son's skin, she goes to Armand and ask him what it means. Note how Armand responds:
"It means," he answered lightly, "that the child is nto white; it means that you are not white."
The vital importance of race to this culture is thus emphasised, and explains the sudden change in Armand's affections and mood. Having become much happier since his marriage to Desiree and the birth of his son, suddenly treats her "coldly" and "cruelly," which leads Desiree to kill both herself and the baby. From his perspective, Desiree has caused him an "unconscious injury" that "she had brought upon his home and his name."
Of course, the irony of the important symbol of their son is that his dark skin colour springs not from his mother, but from his father, as the letter that Armand discovers at the end of the story reveals. The son is therefore an important symbol of race in the story, and how it leads characters to act inhumanely and to be transformed.