After the Choosing Ceremony, Beatrice leaves with the Dauntless crowd (after getting a mad-sad look from dad and a smile from mom, which is weird).
And initiation into the Dauntless starts pretty quickly. To get to their home, Beatrice has to jump on a moving train. (We picture it basically like the El in Chicago—an aboveground train system.)
Beatrice gets on with a little help from another transfer, a girl from Candor named Christina. But she sees another transfer fail to get on the train. Which means he's factionless now. Ouch.
Then they have to jump off the moving train—initiation challenge #2. Another candidate decides he'd rather be factionless than dead, but Beatrice helps Christina jump.
But some other candidate misses the roof and fell to his death. Yeah, they're workin' with live ammo around here.
Beatrice meets Peter who is a Candor transfer and already a jerk. He makes Beatrice feel uncomfortable and calls her a Stiff (which is a mean term for Abnegation.)
And then we get to initiation challenge #3: jumping from the roof into a big hole in the ground. Beatrice wants to show she can be brave, so she jumps first.
There's a net at the bottom (of course, or else it would be a very short book). And Beatrice meets Four, who is an important guy in Dauntless, and who celebrates her for being brave enough to jump first.
She also gets to pick a new name, so she chooses Tris. (Short for Beatrice, but with more attitude.)