So there's this kid who wakes up in an elevator with no memory of his past other than the fact that his name is Thomas. When it the elevator doors open, he is pulled into a huge glade by a bunch of teenage boys who also have no memories besides what they should be called. They all share a strange vocabulary, a fondness for capitalizing words to make them special, and the same mysterious fate.
Thomas gradually discovers that the Glade (see what they did there? Capitalize it and BOOM, you got yourself a name) is run by two boys, Alby and Newt, who maintain order by enforcing strict rules and keeping all of the boys busy harvesting food and whatnot. This is important because outside the Glade is the Maze, a terrifying labyrinth of high walls covered in ivy that houses strange, lethal creatures known as Grievers. So the boys are stuck trying to stay alive as well as "solving" the Maze by running through it as fast as they can while tracking movements of the walls and trying to find an exit.
Then, a day after Thomas's arrival, a girl is delivered through the elevator into the Glade. The boys are stunned, perplexed, worried, and perhaps a little excited to have someone who doesn't smell like day-old socks and Axe body spray (just kidding, geez). However, unlike each of the boys, she shows up mumbling strange prophetic words and then lapses into a coma. To make matters worse, her arrival triggers everything in the Glade to change: the sun disappears, the deliveries of supplies stop coming, and the doors stay open at night which allows the Grievers to pick kids off one-by-one. Oh goodie.
Thomas has a brilliant idea, and figures out that maybe the walls of the Maze aren't moving for funsies, but that maybe their movements are actually a code. So they do an arts 'n' crafts project and discover that the maze is in fact spelling out words. Thomas also discovers that the Cliff that they all thought was just a cliff turns out to be where the Grievers are coming from. If they can come and go through a weird black hole over the edge of a cliff, then maybe so can the boys.
The girl, Teresa, wakes up and tells Thomas that they knew each other before they were put in the Glade and oh, by the way, they can communicate telepathically.
In an act of desperation to get his memory back, Thomas gets himself stung by a Griever and discovers the Griever Hole is indeed an exit. Not only that, the code that the Maze has been spelling out is their ticket to escape.
A large group of them decide to make a run for it, knowing that it could be suicide trying to take on the Grievers but figuring that nothing could be worse than being stuck in the Glade. They succeed, only to find out that what they've been doing is an experiment being conducted by the Creators, a group called WICKED, who may or may not be evil. The boys and Teresa then get "rescued" by some kind of rebel group and brought to a safe haven while being told about "the Flare"—an apocalyptic occurrence that killed off half of the world's population.
The epilogue reveals that the "rebel group" may just be another variable in the experiment, and they weren't the only group being evaluated. We smell a sequel…