Mara, who is 6'2, is best friends with Quinn, who is about a foot shorter than she is. When Mara decides she wants to play football, having been told by her basketball coach that she needs to play a team sport without getting violent with anyone in order to be reinstated on the basketball team, Quinn says "go for it." Quinn is a leading [some football position] on the team, which hasn't had a winning season in years. Mara's brother Noah, is also on the team. Mara finds that she loves the sport; she can get her aggression out on the field, but what she doesn't predict is that a bunch of other girls will join her efforts. 

At first she keeps her distance from them, especially Carly, the uberfemme basketball teammate she punched to get her place on the team in jeopardy to begin with. Carly is the only out lesbian in the high school, and Mara is closeted. 

Mara's story is about learning to deal with her sexuality, with other women, and the reality that she's not one of the guys, and that Quinn is not really her friend. In fact, Quinn is an asshole.