Throughout their senior year in high school, Zoe, Maddie, and Angela continue to share "instant messages" with one another about their day-to-day experiences as they consider college, sex, the importance of prom, and the inevitable end of their inseparable trio.

High school freshman Jane believes that she would do anything to be popular until she is selected to be in the school's most exclusive clique and learns that popularity has a price.

Winnie's thirteenth year brings many joys and challenges as she negotiates her relationship with her first boyfriend and realizes that change is inevitable in her friends, family, and even herself.