In the film The Fifth Wave, the Earth is in trouble, because four successive waves have almost eliminated the population. One of the few remaining survivors is Cassie Sullivan, a teenage girl who only has her younger brother, Sam.
He has to leave it hidden, promising to return. He knows that the only chance they have to survive is that, which does not prevent their heart from breaking. Cassie leaves, but at the time of returning for her brother does not find it.
On the way he meets Evan, a young peasant who is able to hunt. Cassie has seen everything, which has made him distrust the human race, but right now we can say that it is in the hands of Evan.
She wants to find her brother Sam above all things, so if she wants to see him again, she has to trust Evan, which is not funny, since she has seen what men are capable of.