She felt that she had just condemned a man to death.

If Monsieur Peirotte should now be killed, she would always see his ghost at night time.

He would come and haunt her.

So she only ventured to cast furtive glances, full of fearful delight, at the unhappy man's windows.

Henceforward all her enjoyment would be fraught with a touch of guilty terror.
Moreover, Pierre, having now poured out his soul, began to perceive the other side of the situation.