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- "Everything started changing the moment you showed up."
- — Gally to Thomas
In The Fever Code, Gally is introduced as a kid of around ten who helped out in the gardens. Minho enlisted his help with an escape plan, though none of the others (Thomas, Teresa, Newt, and Alby) agreed to come with them. However, their plan was discovered by WICKED, and Minho was punished severely. He beat Gally up at some point afterwards, thinking that Gally's loose tongue probably gave them away. Gally's nose was apparently broken as a result, and it failed to heal correctly.
After Gally had been in the Maze for some time, he one day ventured just beyond one of the Doors in spite of the rules. A Griever immediately attacked and stung him. It was during the subsequent Changing that he regained a few memories.
Gally was despised by most of the Gladers due to his arrogant nature. However, he was the Keeper of the Builders, which must have meant that he was reasonably responsible. Two years after the beginning of the Maze Trials, Gally witnessed the arrival of a teenage boy named Thomas, whom Gally immediately became enemies with, having remembered just enough to know that Thomas had worked with WICKED.
After being interrogated with Thomas by Newt, Minho got into an argument with Gally that ended with Gally running off into the Maze and going missing. After missing for many days, Gally eventually returned to the Glade, scared and dirty, and warned Gladers that the Maze's Creators were going to kill them and that Grievers would take one of them every night. Plagued by a nameless terror as the Grievers attacked the Homestead the first night, he snatched planks barricading windows and hit Newt with one of them. Thus a Griever managed to penetrate the Homestead and seized Gally, running off into the Maze.
Gally was brought to WICKED and kept there for several days. When the surviving Gladers made it through the Griever Hole, Gally emerged from the shadows with a knife, and while under control of WICKED, attempted to kill Thomas by throwing it at him. A young Glader named Chuck jumped in front of the knife and was killed in Thomas's place. Thomas, distraught by Chuck's demise, attacked Gally, punching him repeatedly in the face and severely injuring him. While Gally and Thomas fought, a group of adults entered the chamber and killed the WICKED agents. Thomas knocked Gally unconscious and fled with Teresa and the other Gladers.
In The Death Cure, unknown to Thomas and the other Gladers, Gally was taken into custody by WICKED agents and imprisoned in WICKED's headquarters. During his imprisonment, Gally felt terribly guilty for killing Chuck, even though he had been under WICKED's control. (WICKED had told Gally he would be killing Thomas, which he was fine with, and thus he had not fought their control.) Gally made several attempts to escape, but was stopped by guards every time. However, a group of spies snuck into the facility. They told Gally that if he acted crazy enough, WICKED would believe he had the Flare and put him in a city somewhere in the United States, where Gally and the spies could meet again and Gally could join them.
Gally later sends a message to Thomas, Minho, Newt, Brenda and Jorge, telling them to meet them at his apartment in Denver, where he now works for the Right Arm. He explains to them how he escaped and tells them that WICKED is after them and Hans, the man who can get rid of the implants in their brains. He also tells them that Teresa and the rest have been there, and if they wanted to join the Right Arm after finding them, they should come see him.
When Thomas and Brenda later find Vince, the leader of the Right Arm, Gally is there with him, and he assures Vince that Thomas can be trusted. He becomes part of the "army" that takes the Immune back to WICKED to take it over. However, when the Right Arm is preparing to blow the place up, regardless of any Immunes left in the Mazes, Gally joins Thomas and the rest.
He helps Thomas rescue the rest of the Immunes, going back to the Maze and then fighting against the Grievers and Janson's men before going through the Flat Trans to the last paradise with the Immunes.
In The Maze Runner film, Minho seemingly killed Gally with a spear; however, he was shown moving slightly (possibly breathing) after being impaled. In Maze Runner: The Death Cure, he is revealed to still be alive and in league with Lawrence.
Physical Appearance and Personality
In The Maze Runner, Thomas described him as a fifteen-year-old who was tall and skinny with black hair, green eyes, and a nose the size of a small fist that resembled a deformed potato. His voice was described as being scratchy. Gally was quick to anger while in the Glade, although he was friendlier as a child. In The Death Cure, Thomas and Gally were able to put the past behind them and become allies.
In the films, Gally is portrayed by Will Poulter with dirty blond hair. While an antagonist, he does seem to have some redeeming qualities, as he tries to look out for the other Gladers.
- Gally is the only character to appear in both The Maze Runner and The Death Cure, but not in The Scorch Trials.