We start off, appropriately, in Part 1: "Turning Pretty."
Tally Youngblood is all alone because she's still an ugly and her best friend Peris has already been turned pretty.
So she busts out of the ugly dorm (leaving her interface ring behind, since that tracks her movement) and breaks into New Pretty Town (the part of the city where the new pretties are).
Tally and Peris used to do this all the time to watch the stupid new pretties at their stupid parties (so stupid, not that Tally was jealous at all); they would take an old bridge that's not connected to the security system (unlike the new hovering bridges, which constantly report what you're listening to on Spotify to Facebook).
Like that time when their rope slipped and splashed them into the river. Good times. (Seriously, those were good times because she was miserable and wet, but with a friend.)
But Tally is going to break further in to New Pretty Town because she wants to talk to Peris, who is supposed to be her best friend forever. She has the scar on her hand to prove it, from that time they scarred their hands together.
Now, uglies do tricks and pranks all the time, but this seems like pretty serious rule-breaking to Tally, so she wants to remain hidden. But since Tally is still an ugly, she'll stick out like a sore thumb in New Pretty Town—an ugly sore thumb.
Pretties spend all their time partying, which means that Tally is going to run into a lot of people in New Pretty Town in varying states of drunkenness, from pretty sober to Lindsey Lohan. (We're sorry, Lindsey, we loved you in Mean Girls.)
Luckily for her, Tally runs into a big street party that includes a giant machine that's throwing around masks while it plays the drums. Weird.
So Tally grabs one of the masks to hide her ugly face. And here's a big neon sign that says "IRONY" because the mask she gets to hide her ugly face is a pig mask.