Kathy (Chloe Grace Moritz) lost her mother in the third wave of attacks, and her father (Ron Livingston) took her and her younger brother Sam (Zackary Arthur) to take refuge in the refugee camp. When the soldiers entered the refugee camp, they immediately thought they were saved. Colonel Voss (Liev Schreiber) claimed that they had come to help the refugees, and that the army would give priority to protecting them with all the children and then come back to rescue the adults. Kathy's father reluctantly agreed to let the two children leave with Voss's army. Because Sam forgot to bring her beloved teddy bear, Kathy went back to the refugee camp to look for it. As a result, before she came back, the bus left with the other children, and the brother and sister were forced to separate. After returning to the refugee camp, Kathy and other refugees soon discovered that aliens can live in human bodies, so no one can trust them. But the soldiers and other survivors had a heated argument about what to do next, which led to the army killing all the refugees. Kathy managed to escape and vowed to save Sam.