The front hall and the outer doorway form the threshold between the unstable family life and the outer influence, namely Krogstad, that threaten the balance further.  Ibsen's entrance  sets up the contrast between the innocent and childish appearance that Nora constructs for herself inside the house and the serious legal reality of her situation outside the house.  Krogstad's first entrance, standing at the door, the threshold to the outside world - which he explains by saying that the outer door "was ajar; it must have been that someone forgot to shut it" (1577) - shows Krogstad's power to invade Nora's world with the greatest of ease.