Read it through once

Sometimes when some outrage of peculiar offensiveness stung her to the heart, she would plan schemes of vengeance and revel in the fancied spectacle of his exposure to the world as an imposter and a slave; but in the midst of these joys fear would strike her: she had made him too strong; she could prove nothing, and--heavens, she might get sold down the river for her pains! So her schemes always went for nothing, and she laid them aside in impotent rage against the fates, and against herself for playing the fool on that fatal September day in not providing herself with a witness for use in the day when such a thing might be needed for the appeasing of her vengeance-hungry heart.