Thomas is the main protagonist of The Maze Runner series. He is portrayed by Dylan O'Brien, who later plays Mitch Rapp in American Assassin and Joel Dawson in Love & Monsters.
The Maze Runner
At the start of the film, Thomas wakes up in the Box and then arrives in the Glade with several other teenagers. He meets Alby, Chuck and Newt and learns that beyond the walls there is a maze populated by dangerous creatures. In the evening, he remembers his name is Thomas and has dreams where he is in a laboratory.
The next day, he is attacked by Ben, a runner who has been stung and is banished into the maze. The next day, Thomas enters the maze to rescue Minho and Alby. He helps hide Alby in the vines and confronts a Griever whom he kills. He then manages to bring Alby back to the Glade with Minho.
During a meeting, Gally complains that Thomas entered the maze, breaking one of the three rules. Minho ignores what he says and suggests making Thomas a runner. At this moment, Teresa, a girl is brought to the Glade. Thomas, more and more curious, decides to return to the maze for more answers and Minho accepts recruiting Winston, Frypan and Zart. Together, they dissect Griever's corpse and find some sort of battery which they show Newt and Gally. The latter does not trust Thomas and Newt formalizes him as a runner. He later meets Teresa and heals Alby with a serum Teresa had in her pocket.
Being taken to the Pit for one night, Chuck keeps him company and shows him an object he has carved for when he reunites with his parents. The next day, he sets out again in the labyrinth with the Griever beacon and discovers their hole which could be the exit of the maze.
Night falls and the doors of the Glade remain open. The Grievers then show up and kill several Gladers including Alby, Zart and Clint. With a Griever syringe, Thomas injects it himself and recovers his memories. After being locked in the pit with Teresa again, Thomas reveals that he worked for WCKD but ultimately betrayed them. Encouraged by Newt who tells him to forget the past, he hatches a plan to deal with Gally, who has taken power, and go into the maze. Several Gladers follow him and all together fight the Grievers of which three teenagers die.
After which, the group discover WCKD's abandoned lab where Ava Paige explains that the maze was a test and that the Gladers are immune to a virus that has destroyed the entire world. Following the message, an airlock opens and when they are about to leave, Gally stops them, stung by a Griever. He is about to shoot Thomas but Chuck intervenes and Minho throws a spear in his chest. Chuck then dies under the eyes of Thomas and the others, then hooded soldiers take the Gladers out of the lab.
Outside everything is desert and the group is taken in a helicopter, far from the labyrinth actually designed by WCKD.