The first few seconds of the trailer establish the fact that Thomas doesn't remember anything but his name, in terms of an introduction to the fictional universe he inhabits this put the audience on the same level as him. This allows his introduction to be our introduction which is useful for explaining the concept of the story for those who don't have prior knowledge of the books. for just over a minute the trailer effectively takes the form of a question and answer session to explain the principles of "The Maze". Once that has been set up Thomas starts to question the norm and a change is thrown into the mix, when a girl appears saying Thomas' name. This second section shows that we have been introduced to the glade on the edge of change and also sets Thomas apart, as one glader says "Everything started to change when you showed up.". However before the animosity builds against him too much the danger levels reach critical for them and they're forced to turn to him for leadership. This trailer basically acts as a plot synopsis, establishing the fictional universe and it rules before showing us its degradation which will make up the plot of the film. In a way this trailer is a taster which will give audiences an idea of what they're buying into.
 As this film has quite a large ensemble cast it takes a bit of time to start to introduce us to some of the key characters other than Thomas, the first person we see beside Thomas is Will Poulter's character, who like all the others remains unnamed in the trailer. This suggests that he will be very important to the storyline as he is shown clearly and has spoken lines, the recognizable actor also implies this. the next one introduced is the guy who says "Welcome to the glade" his importance is shown through the fact he informs both Thomas and us of the the place's name, his voice is also the one questioning Thomas on who he is at the beginning which gives him an air of authority. His role as the group leader is further confirmed by the fact he is answering Thomas' questions and giving orders. However when thomas asks about the maze the narrative role switches to another boy, again played by a recognizable actor Thomas Brodie-Sangster,  as these two are shown talking in a two shot it seems like they are the same in the hierarchy and makes it seem like more of a conversation between friends. We don't learn much about the girl in this trailer however she seems to be keen to continue pushing Thomas apart from the rest suggesting she might know something.