Describe what Newt showed Thomas early that second morning? Why did he do this?

In Chapter Six, Thomas is jostled awake by Newt, who tells Thomas that he has to show him something before everyone else is up. Newt leads him to the courtyard and breaks out into a run. Thomas follows, running as well, unsure if he can trust Newt or not but knowing he has little choice. Newt leads Thomas to one of the walls and pulls back the vines that grow on it, revealing a small window.

Newt tells Thomas that they want to show him why the walls close every night and why he should be glad that he is on this side of them. Thomas can make out something moving outside the window, giving off a strange light. He puts his face to the window and sees a large, bulbous creature about the size of a cow. It is a hideous mix of machine and animal. Its appendages are adorned with instruments like buzz saws and long rods. It charges the window, sending Thomas to the floor. But the window holds. Thomas asks Newt what they are. “Grievers”, he answers.

Thomas is no longer sure he wants to be a Runner. Newt tells him that he now knows what is in the Maze and that he is expected to help them. “What’s that?”, asks Thomas. “Find our way out, Greenie,” Newt says. “Solve the buggin’ Maze and find our way home.”