That's The Plan
Thomas lay in his hammock that night feeling sick.
Ben’s eyes were seared into his mind, stabbing arrows. His words were cruel, but ever so true. He had forgotten how much shit he had gone through in the Glade, all of it overtaken by stuff that had happened in the Scorch, or in The Last City. What happened next?
Oh, yeah. He’d run into the maze to save Alby and Minho, and then they’d get trapped over night. They would all survive, and then Teresa would come up, with two cures to the Sting.
Thomas had used one of them, but he didn’t need to get Stung anymore. He already had all the information he had discovered during his nightmarish Stinging haze.
All he had to do was make sure that the Gladers didn’t let Ben be sacrificed. He’d let Alby get Stung, and once Teresa came, they could inject Alby and Ben with the syringes.
Besides, there was no way he could persuade Alby to stay in the Glade. And he also had to make the Gladers believe in him. Surviving a night in the maze would help - not like there were other choices.
Plus, maybe if Ben (Gally’s best friend) survived, then Gally wouldn’t go fucking insane and murder Chuck. Just mabe.
And if he got Ben onto his side, then Gally would follow.
It was all wishful thinking, but the resemblance of a plan began to form in his head.