When an explosion rocks David and Will's suburban high school one morning, a deadly virus is unleashed on the school. The virus only infects teenagers in their peak puberty years, making them lethal to adults and children until they finish adolescence. Within minutes, every faculty member is dead. The military quarantines the building, opening fire on anyone attempting to escape and installing bi-weekly food drops.
 
After a year of quarantine, with no adults around, the students have created their own society. All of the social cliques have developed into gangs--The Nerds, The Geeks, The Freaks, The Sluts, The Skaters, The Burnouts, The Pretty Ones, and The Var­sity--and each gang provides a service with which they can barter for provisions. Without a gang, it's almost impossible to secure food, water, territory, or supplies.
 
David and Will float just under the radar, until one day David sees his brother's long-time crush, Lucy, about to be attacked by a Varsity jock. Impulsively, he steps in to protect her, and winds up accidentally killing The Varsity member. Suddenly, the whole school is on the lookout for David and Will. How will the brothers survive and what will happen once David no longer carries the virus?