What becomes of Desiree and her baby?

When Desiree's husband discovers that his child is half African American, he tells Desiree to leave.  She walks off the plantation, not using the road but seeming to head in the direction of her parents' place.  However, Chopin writes, "She disappeared among the reeds and willows that grew thick along the banks of the deep, sluggish bayou; and she did not come back again."  This line indicates that Desiree and her baby end up drowning in the bayou, which is a marshy lake common to Louisiana.  
That is not where the story ends.  Chopin takes the reader back to L'Abri, Armand's plantation, where he is burning all of Desiree and the baby's belongings.  In that inferno, Armand has also put a letter from his mother to his father, which indicates that she was of African-American heritage, and his father knew this and married her anyway.