As season three of the hit series begins, Ryan, Marissa, Seth and Summer are starting their senior year of high school. But after last year's shocking events, Marissa finds she has been knocked off her pedestal, further straining her relationship with Ryan. Plus, Kirsten befriends a mysterious woman (Jeri Ryan), in rehab. Other guest stars include Eric Mabius, Autumn Reeser and Nikki Reed.