The Fever Code is a 2016 young adult dystopian science fiction novel written by American author James Dashner and published on September 27, 2016, by Delacorte Press.

The Fever Code is the second book, chronologically, set in between the events of The Kill Order and The Maze Runner.

In the narrative's main plot, Stephen is introduced and has been renamed Thomas by the people in the organization WICKED (World in Catastrophe: Killzone Experiment Department).

He has to go through blood tests and advanced classes and soon meets Dr. Paige, who acts as a parent to him, and he soon becomes her favorite.

Not being able to answer truthfully about the Maze being his project only makes Thomas's friends more suspicious, and eventually angry.

Dr. Ava Paige explains what happened to George and reveals that the Grievers have a virus similar to the Flare.

It is then revealed that Teresa was originally the young girl Deedee, who survived in the prequel The Kill Order.

Thomas has come to believe that a cure will never be possible, feels that his friends are then suffering unnecessarily, and vows to save them.

He begins with an idea to insert the elite candidates into the Maze with their memories intact so that they can rescue the Gladers, but Teresa seems reluctant.

The book ends with him standing up in the Box with his memories gone, which set the events of the main series in motion.