In her story that concerns itself with one hour in the life of a transformed woman, Kate Chopin describes the death of Louise Mallard as "a joy that kills." This phrase implies that the momentary freedom that Louise has experienced, a freedom in which she has felt a certain triumph, has been taken from her when Bently Mallard turns his latchkey and enters the room.
It is not that Mrs. Mallard does not love her husband; on the contrary, this is her "joy"--that she realizes he is yet alive and not killed in the train crash, as previously believed. However, with this realization that is joyful comes the tragic knowledge that her new vision of
a long procession of years to come that would belong to her absolutely
will not come to fruition; and, it is this realization that her self assertion which she feels is the "strongest impulse of her being" will never be afforded an opportunity that kills Louise Mallard.