Redo on The Scorch Trials: Theme and Summary

This is a redo for a Theme and Summary of The Scorch Trials, the book follows upon the first book which was The Maze Runner. The books about a character named Thomas who has to overcome a series of obstacles, trying to make new friends while trying to stay alive. After the events from the first book, the girl that first came out of the elevator, I can't recall of what happened to her, but some of Thomas's more closer friends such as Teresa, is the only thing that he has left. For a thematic statement, mine would be not all relationships last forever. This would be my thematic statement because throughout the course, almost every relationship with someone that Thomas gets doesn't end up well like with the coordinators that set up the wasteland? And the gladers, a group formed in the first book, they weren't very close, but it doesn't get any better. At first, he makes many temporary allies, one of them which was a friend of Teresa, she wasn't very trustworthy. But even his closest friends betrayed him. I just wonder what would happen in the next sequel.