Peter Jaxon is the younger brother of Theo Jaxon and a member of the First Colony. As a member of the Watch, he is a trained fighter, experienced at killing virals. He is one of the First Colonists who flee with Amy.
Peter first encounters Amy at the Carousel in the mall near the Colony. She saves his life, initially communicating with him telepathically because she doesn't remember how to speak.Later she tracks him and the other members of his party back to the Colony.
Peter suffers from an inferiority complex, convinced he is not as strong or capable as his brother and sure his parents felt the same way. Eventually he learns from Auntie that his mother believed he was much stronger and more resilient than his brother, leading to his taking on more responsibility. Over time his personality darkens, as those responsibilities weigh heavily on his mind. He loves Alicia Donadio, who trusts him implicitly.
After the defeat of Babcock, Peter tries to infect himself with the serum made from Amy's blood, in the hope that he will survive and be able to more effectively fight the rest of the Twelve.
Peter returns to Texas and joins the Expeditionary.