The character, Teresa Agnes, is introduced as a secondary protagonist in the first Maze Runner book, with the final installment, The Death Cure, proving to be hugely significant as it marked Teresa’s death. In the events preceding her tragic demise, Teresa goes through a lot - from surviving the maze to even being forced to betray her own friends. Even though the films don't stay true to the books, removing her telepathic connection with Thomas, they do add a lot of emotional depth to her character, capturing her moral dilemmas as the Gladers take down the evil corporation Wckd.

As the cast ends their run in The Death Cure, Teresa’s death naturally serves as a major shock given how significant of a character she has been in the trilogy. Given her actions in The Scorch Trials, it becomes difficult for Gladers, such as Thomas, Newt and Minho to forgive or trust her again.