The film follows a 37-year-old man named Mike O'Donnell (played by Matthew Perry) who becomes his 17-year-old self (played by Zac Efron) after a chance accident. In 1989, 17-year-old Mike O'Donnell is a star athlete with a bright future. However, his life takes a turn for the worse when he learns that his girlfriend, Scarlet Porter, is pregnant. Mike abandons his dreams of going to college and playing basketball professionally to be with Scarlet.
Twenty years later, Mike is a divorced and unfulfilled man. He is estranged from his children, Maggie (played by Michelle Trachtenberg) and Alex (played by Sterling Knight), and his job is going nowhere. One day, Mike has a chance encounter with a janitor at his old high school. After saving the janitor from falling off a bridge, Mike is magically transformed back into his 17-year-old self.
At first, Mike is thrilled to be young again. He enjoys the attention he gets from his classmates and the opportunity to relive his high school glory days. However, Mike soon realizes that being 17 in the 21st century is not what he expected. He struggles to fit in with his children, who are now teenagers themselves. He also develops a crush on his former girlfriend, Scarlet, who is now the guidance counselor at his high school.
As Mike navigates the challenges of being a teenager again, he begins to appreciate the things he took for granted in his first life. He learns to connect with his children and rekindles his relationship with Scarlet. Mike also rediscovers his passion for basketball and leads his high school team to the championship.
In the end, Mike learns that there is no such thing as a perfect life. However, he also learns that it is never too late to make changes and improve your life.
