Both Desiree and Armand are experiencing a binary oppostion individually and one as a result of their failure to communicate.

Armand knows his wife Desiree's baby is black, but he is not admitting it.  He is, however, treating Desiree as though she has betrayed him as he believes that she has. His binary opposition is between what he believes to be true and what he is to do about it.  On the other hand, Desiree know she has not cheated on her husband, but she is sure that her husband believes she has.  She does feel confident to oppose him thus creating a binary opposition in what she knows and her own presumed inferiority. 

It could be argued that another binary opposition is created by the silence of both Armand and Desiree--neither expresses themselves, so both Armand and the reader are surprised at the end.