"'It's you who are responsible.'"
The Old Woman recounts that these are the couple's son's final words to them as he left, which occurs in Part Three. The son's story beforehand—about his parents' killing birds—makes little sense, so his labeling them responsible seems, at first reading, to be a throwaway line. But it can also be read as an ironic comment, in that the parents are not, in fact, responsible. The Old Man and Old Woman create fantasy lives to escape their real ones, they regret the past but do not take accountability for it, and the Old Man is not able to deliver his own message but relies on the Orator. The existentialist philosophers believed that only by taking responsibility for one's life could man's absurd condition acquire meaning. Everything we see of them suggests that the couple is not, in fact, responsible, and their meaningless life, one of illusion and grinding routine, is their own fault—just as their son's departure is most likely their fault, despite whatever we make of the bird story.