Allie Pennington (Britt Robertson) is ecstatic when her parents tell her she will be staying at Avalon High until she graduates. She can finally join the track team, make new friends and be a normal high school student. But shortly after arriving, Allie discovers that something strange may be afoot. While researching a term paper on King Arthur’s legacy, she begins to notice some interesting parallels between the past and the present – from handsome quarterback Will (Gregg Sulkin), his cheerleader girlfriend, Jen (Molly Quinn), and their best friend, Lance (Chris Tavarez), to Will's brooding step-brother, Marco (Devon Graye), a quirky kid named Miles (Joey Pollari) and football players who act like knights of the roundtable. The deeper Allie searches, the more convinced she is that her school is a contemporary Camelot, and it's up to her to solve the mystery of Avalon High before notorious traitor Mordred wins again.