Content Warning: This section of the guide discusses child sexual abuse, the death of a child, murder, violence, domestic violence, suicide, and rape. 

Blue Mouse is Olivia Land’s beloved toy that disappeared along with her when she vanished. It serves as a symbol of Olivia herself, as well as a reminder that the evil she endured must not be forgotten. Jackson describes it as a “doll” that was “made of some kind of grubby toweling material and had long thin legs and arms and the head of a mouse” (89). Though Olivia is never forgotten by her sisters, it is Blue Mouse’s reappearance in their father’s locked desk drawer that causes them to hire Jackson to find out what happened to their sister. Blue Mouse’s presence is an insistent reminder that the truth about Olivia must be uncovered.

Blue Mouse also helps Jackson solve the case—he watches people’s reactions to the toy. When he shows it to Sylvia, he understands that she knows more than she has admitted to: “The thing about Sylvia was that she hadn’t really been surprised to see Blue Mouse. It was as if she’d been waiting for him to turn up eventually” (376). Sylvia also doesn’t ask Jackson where he found Blue Mouse.