Lillo wrote many short stories (collected in two major books, Sub Sole and Sub Terra) which sparked the interest of social activists who were appalled by the conditions in the mines.
At the story's end there is a strong contrast between the clean, pure and benevolent sky, and the underground monster that devours the humans who dare to penetrate its dark lair.
His mother, who has lost her husband and two other sons in similar accidents, cannot emotionally deal with his death and dies in a suicidal jump into the mine, personified as a monster who consumes humans.
The group parted and many faces turned toward the woman who, with her head on her chest, deep in an absolute trance, seemed absorbed in contemplating the abyss open at her feet.No one ever understood how she managed to jump over the barrier or the retaining cables.
A few seconds later, a low and distant sound, almost imperceptible, erupted from the hungry mouth of the pit along with a few puffs of thin vapor: it was the breath of the monster gorged with blood in the depths of his lair.