“Had I forgotten? Memories of Mum, uncomfortable ones, flood my mind and I push them away quickly. It isn’t the same, I tell myself fiercely, I am not the same. By tomorrow, I’ll have remembered.”

This line reveals, through subtext, an important part of Cass’s backstory: Her mother’s dementia created an enormous strain on her family and showed Cass an example of an illness she desperately doesn’t want to live through. Cass’s fear that she’ll develop dementia, like her mother, makes her vulnerable to Matthew and Rachel’s psychological manipulations, which weaponize Cass’s sense of memory fragility against her.

“For the hundredth time, I find myself wishing that Rachel and Matthew liked each other more.”

Because The Breakdown is narrated from Cass’s point of view, the reader has access only to Cass’s perception of reality. This allows the author to mislead readers without violating their trust, using false bits of information, or red herrings. Cass thinks Matthew and Rachel don’t get along, so she’s unlikely to suspect that they’re having an affair and scheming against her. Her belief makes the truth less apparent to readers, thereby maintaining mystery and suspense.

“I know it’s stupid but I feel as if it’s my fault she’s dead. Tears prick my eyes. I can’t imagine the guilt ever going away and the thought of carrying it around with me for the rest of my life seems too high a price to pay for a moment’s selfishness. But the truth is, if I’d bothered to get out of my car, she might still be alive.”

Like Cass’s fear of dementia, her guilt over Jane’s death is a crucial factor in the circumstances that make her vulnerable to gaslighting. Guilt is also a meaningful character trait that creates depth and complexity in the story’s protagonist. Additionally, Cass’s interaction with Jane just before Jane’s death and Cass’s guilt over it prompt a central conflict that shapes the plot and her character arc.