How does the author use foreshadowing in The Verge?

Claire foreshadows her own fate very early in the play when she speaks the line, "Things that take a sporting chance, go mad." She does not necessarily believe that madness is a terrible thing. For Claire, it is her only chance of breaking free. If Claire cannot recreate the outside world in which she lives, she must turn to the only word she has total control over, her interior one. For Claire, madness is the ultimate welcome escape. She sums up this paradox with the line, "Madness that is
the only chance for sanity."