It's me, Gally.

Prologue

He was an enigma to everyone there.
Despite the time he had spent with them all – almost three years – no one knew what exactly made him so hostile and agressive. Many guessed that it was merely a character trait he posessed , or simply the way he had always been. They had tried to ask him a few times, but he never gave a clear answer. He just vaguely muttered something about a Griever and W.I.C.K.E.D, whatever that meant.
It wasn't until they all went through the Flat Trans to Paradise, that his demeanor changed. He started talking to people more, trying to socialize and maybe even get friends.
The first true friend he made was perhaps, the most unlikely of all the Gladers for him to befriend – Thomas.

Thomas thought Gally was is the kind of person that's been neglected and judged as a child, which led to his blatantly agressive nature. He had learned to ignore Gally pretty well – until he killed Chuck, of course – but in the Scorch he didn't give a second thought to him. When he'd discovered that Gally was alive in Denver, he was slightly relieved even though they were basically former enemies in the Glade. Afterwards Gally helped Thomas get to the Right Arm's hedquaters where he and his colleague devized a plan to infiltrate the W.I.C.K.E.D headquaters and destroy it.
After they all went thorugh the Flat Trans Thomas's interpretation of Gally changed – it was as if his mind had gone all blank – and the only question on his mind was one that he thought he had already gotten an answer to. Upon looking deeper however, he realized that the question had remained unanswered through all that time
How could I have been so blind, he thought.
It was a mystery that made him want to recap all the times he had interacted with Gally to answer the question that eveveryone had asked, yet never answered.
Who is Gally? Who is he really?