Before the boxing matches, Christina points out Peter and his friends a.k.a. minions of evil, Molly and Drew. They were all Candor, but they weren't very nice or truthful, so they transferred. And they all know that Christina hates them.
Meanwhile, nice Al beats up Will in the boxing ring, but feels bad about it.
And Eric and Four argue over the meaning of bravery, and whether it's brave to accept inevitable defeat. This is a very full chapter, philosophically speaking.
The fights are supposed to be to unconsciousness, but when Molly beats Christina, Christina tries to concede. And since Eric the Cruel is the one training them, he decides to make a lesson of her.
He orders her to climb over the railing and hang over the chasm at the bottom of the Pit for five minutes. So she does, even though it's hard to hold onto the slippery metal railing (especially after she was just beaten up).
Tris wants to help Christina, but is also a little afraid of being punished.
But when Al starts to chant encouraging remarks to Christina (like "don't fall and die"), Tris starts yelling with him, as if they're cheering on a sporting match. So, that's at least something.
Christina survives the five minutes without any other help from Tris and Al, though they do help Christina back onto the ground—over an objection from Eric the Psycho.