Set in the inner-city of Memphis, Undefeated chronicles the Manassas Tigers' 2009 football season, on and off-the-field, as they strive to win the first playoff game in the high school's 110-year history. A perennial whipping boy, in recent decades Manassas had gone so far as to sell their home games to the highest bidder, but that all changed in the spring of 2004 when Bill Courtney, a former high school football coach turned lumber salesman, volunteered to lend a hand.

The final episode portraits his adventure in joining a Major League Soccer team in Miami and features well-wishing messages from fellow football stars like Neymar and Lionel Messi. The transition from football to his new endeavors is a central theme, and the episode captures Beckham's passion for staying active and engaged beyond his playing days. It concludes with a lighthearted moment of Beckham giving his son Romeo a football lesson, and a playful interaction between them, where Beckham humorously reflects on his successful career at 47 years old.