The Breakdown

Though Cass may think having an alarm system installed in the house is her own idea, Rachel suggests it to her, and Matthew then reinforces the suggestion. Cass is later unable to feel a sense of security because Matthew makes her believe she can’t remember how to use it correctly. She fears his frustration when she sets it off by accident, so she often doesn’t even turn it on. The irony that the alarm, which is meant to ensure Cass’s safety, is suggested by the two people she has the most reason to fear imbues the alarm system with symbolic meaning. Like Matthew and Rachel’s deceptive portrayals of support and loyalty, the alarm system represents a false sense of security. This is especially true for Cass, whose enemies are those closest to her, those who share her home or who she welcomes into it.

In Chapter 14, Matthew and Rachel use a knife to terrorize Cass. Matthew believes it’s a knife that merely resembles the one used to murder Jane. Rachel knows the truth—that it actually is the murder weapon—but its resemblance is all that matters to create the association in Cass’s mind. The intent is to make her believe that it’s the killer’s knife and that the killer is targeting her and then remove it and convince her that it was never really there.