After Nagini left, Tris's life returned to normal. At least, that was how it looked on the surface.
He wanted to see how well the plot could repair itself if he stopped stirring up trouble.
The answer was: very well!
Following his advice, Draco had threatened Harry and the others and actually joined their dragon-raising team, but the little dragon had still been sent away in the end.
Only this time, Draco hadn't leaked the secret. A Hufflepuff boy named Zacharias had.
Before coming to Hogwarts, Tris hadn't even known his name. Although he had noticed the boy's lively participation in class since arriving, he hadn't expected him to quietly set off something this big.
The Norwegian Ridgeback, named Norbert, had been sent to the French Dragon Reserve where Charlie worked, while Harry, Ron, Draco, and Hermione had been punished by Professor McGonagall and sent to investigate the Forbidden Forest with Hagrid.
After some hesitation, Tris decided not to follow them in secret.
Without him there to stir things up, events followed the original plot almost exactly.
In the Forbidden Forest, Harry had encountered Quirrell, possessed by Voldemort, attacking a unicorn, and had been rescued by a centaur. The centaur had told him about Voldemort's return and his designs on the Philosopher's Stone.
He had also said a whole load of strange things that Harry couldn't remember well enough to repeat to Tris. Still, Tris had a vague feeling that the centaur had been running his mouth about him.
Harry had been stunned by these revelations, then started suspecting Snape without a moment's hesitation.
Even though Snape had now been proven innocent of casting the curse during that Quidditch match, the rotten things he did every day made it all too easy to hate him.
Besides, whether intentionally or not,