This is book number 3 in the Quarantine series.
Readers of The Maze Runner and Divergent will devour this dark survival series that's Lord of the Flies in a 21st-century high school setting.
In the third Quarantine book, David and Will are alive...but on the outside of McKinley High. Lucy is the last of the trinity left inside, where Hilary will exact a deadly revenge before taking over McKinley and bringing one final reign of terror to the school before the doors open for good. But the outside world is just as dangerous for carriers of the virus.