Snowballing
"My lie had snowballed into fact already while my back was turned" - Chap (Ch. 2).
As Cassiel begins his charade, the lies he tells start to grow on their own, quickly spreading beyond his control. His family is contacted, then he has to escalate his acting when he meets them and begins living Cassiel's life, then he goes downtown and his presence is announced to everyone. This snowball effect seems to be supporting the idea that deception isn't worth it, since the consequences soon spiral out of control.
Ants on a Dropped Lollipop
"Through the window I could see the playground, kids moving all over it like ants on a dropped lollipop" -Chap (Ch. 3).
In this sentence, Chap is looking outside the window of his Grandad's mostly empty house. He compares the children scampering over the playground equipment to ants devouring a dropped lollipop, emphasizing their smallness and intensity of purpose. Interestingly, there is a parallel between the dropped lollipop and Chap's feeling of being "thrown away" or abandoned when dwelling on his memories of his time at Grandad's house.
Grandad's House
“Those were my places: the weed-run garden, the other twelve rooms, and the arctic upstairs, lifeless like a museum or a film set; a perfect timepiece, fallen into quiet and fascinating ruin" - Chap (Ch. 3).
This is Chap's retrospective impression of Grandad's house; a large, sparse, mysterious anachronism. The metaphor of a timepiece in quiet ruin emphasizes Chap's feeling of this previous time as a kind of previous, no-longer-attainable blissful life.
The Knife-Edge
"I wished for what Cassiel Roadnight had. I wished with every single breath.
I didn't think about the knife-edge that being him would force me to live on. I failed to see it. I refused to look down" - Chap (Ch. 2).
When Chap assumes the role of Cassiel, he has to pretend to be someone he isn't. He has to act well enough to convince even the missing boy's mother and siblings that he is their returning family member. This anxiety and terror about being found out forces him into a precarious psychological state, like living on a knife-edge. One false move and he could fall off (i.e. be found out and lose everything).
The Cage
"It was like being on camera, it was like acting in a never-ending play, it was like living in a cage" - Chap (Ch. 13).
The anxiety of having to act as someone else, mentioned in the previous simile, takes its toll on Chap. Farther along in the book, in Chapter 13, he finds that his façade-based life is exhausting. The constant performance turns his life into a sort of cage that traps him in fear.
