Fifteen-year-old Daniel has followed in his parents' footsteps as the Alien Hunter, exterminating beings on The List of Alien Outlaws on Terra Firma, but when he faces his first of the top ten outlaws, the very existence of Earth and another planet are at stake.

After the mutant Erasers abduct the youngest member of their group, the "birdkids," who are the result of genetic experimentation, take off in pursuit and find themselves struggling to understand their own origins and purpose.