"When you're five years old, trust is another name for love."
This eerie quote explains why Ian's abuse is so effective. He's in a position not just of authority in his family but of trust. As the father, he is supposed to look out for and love his children, not abuse them. Because the child's brain is wired to trust paternal figures, his kids implicitly don't understand the abuse.
"Evil shouldn't triumph."
This is Dylan's rationale for his plot to murder Ian. He believes that Ian is evil through and must be stopped at any cost, but he cannot seem to weigh the motivation against the action itself. Dylan is attempting to make a wrong right by making his own, ultimately undoable, wrong.
"Kirsty Beal sits on the edge of the bed, leaning over Mrs. Beal. 'It's all right, Mum, he's gone now.'"
In this excerpt, the power dynamic between parents and children in the Beal household is revealed. Because her mom cannot cope with her ex-husband's abuse and her own guilt for his abuse, she relies upon her eldest, Kristy immensely. Kristy takes it upon herself to become her mother's emotional support and a role model to her siblings, but she is only fifteen-years-old and hardly capable of managing that kind of responsibility mentally, even if she possessed the necessary maturity.
"He turns quickly and instead of the little marsupial, it's the images from inside his head inhabiting the orange bag. It's not a length of pipe in his hands, its revenge, its punishment. It's perfect."
Dylan is so consumed by his anger against his father, misdirected at Ian, that he can deliberately pretend the events in front of him aren't happening. He kills the possum while imagining it was Ian, but really his brain is playing out a revenge scenario against Dylan's own father.
