The woman who tried to kill Carl's father and herself as his birthday present, and half succeeded.
Standing in the trainyard after Fire Brandy and Tizquick rode The Nightmare Express to their deaths — Brandy to stop losing children, Tizquick because his daughter had been a lie — Carl thought of his own mother. She had attempted to kill his father and then herself as a goddamned birthday present to him, and she had only half succeeded. The memory sits directly beside his realization that, at the edge of the apocalypse, he finally understood how much he needed other people.
Not described in this chapter.
Carl's source of inherited grief, surfaced by the two NPC suicides.