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…