Ryan, Marissa, Seth and Summer are about to begin their senior year at The Harbor School, but while everyone else celebrates the last days of summer, a dark cloud hangs over the foursome. Two months after being shot, Ryan's brother Trey still clings to his life, and the police want to know who really shot him. As Julie and Jimmy are determined to protect their daughter at whatever cost, Ryan considers taking the fall for Marissa. Seth, Ryan and Sandy try to fend for themselves at home, while Kirsten, in a plush rehab centre, befriends a fellow recovering alcoholic, Charlotte Morgan, who may not be everything she appears to be.