As the gang returns to school for their senior year, Jack Hess, the new dean of discipline of Harbor High School, wants to expel both Ryan and Marissa for the shooting incident. Summer fights with the annoying and overachieving Taylor Townsend over being Social Chair for planning the school activities. Meanwhile, Kirsten worries about leaving rehab, while Charlotte inspires her to shack up with her, and when Sandy learns that Kristen left rehab without informing him, he becomes worried about Charlotte's influence. Jimmy worries about his business 'partner' Don who wants to collect for money he owes in overdue business investments.