LitCharts assigns a color and icon to each theme in The 5th Wave, which you can use to track the themes throughout the work.
Trust and Belief
Survival and Perseverance
Warfare and Dehumanization
Family
Summary
Analysis
Once a week, Cassie goes scavenging with her M16 gun for necessities like bottled water. It’s currently a time called the 4th Wave, and Cassie doesn’t trust anyone she sees—her dad’s death taught her to suspect even strangers who look harmless. Cassie feels that her inability to trust anyone is causing her to turn against other humans—and perhaps a similar distrust has torn society itself apart. But then, by an abandoned store, she sees a figure who is badly hurt—or at least looks that way.
The novel is not just about the physical difficulties of living through an apocalypse but the mental toll it takes on a person. For Cassie, her biggest problem is that she feels lonely, but she can’t find companionship because every new person she meets is a potential threat. As this chapter shows, even someone who appears to be gravely injured may still be setting some sort of trap for her.