The expedition
(Book)

"Drayden and his friends thought nothing could be harder than the Initiation. Little did they know it had only been a warmup for the challenge that lay ahead. With New America's situation dire, Drayden and the pledges venture out into the unexplored world outside the walls, escorted by a team of elite Guardians. The group seeks to contact another civilization in what remains of Boston, but Drayden has secret goals of his own. Dangers abound in the real world, including Aeru, the deadly superbug that wiped out humanity. While they battle the elements of a desolate landscape, a power struggle emerges within their ranks. The Guardians seem to be carrying out a covert mission themselves, and the quest turns everything they thought they knew about New America upside down"--Goodreads.com