Liverpool in the fifties: John Lennon (Aaron Johnson), 15 years old and fed up with school, falls apart at home with his strict aunt Mimi (Kristin Scott Thomas). One day, however, John meets his mother Julia (Anne-Marie Duff) again, who had left the then five-year-old in a hurry. The fun-loving, music-loving woman introduces John to the exciting new world of rock 'n' roll and teaches him to play the banjo - unaware that she is laying the foundation for Lennon's later life. John forms a band and meets the talented guitarist Paul McCartney (Thomas Brodie Sangster) through friends. But the balancing act between his musical ambitions and the two strong women in his life becomes a real test for Lennon ...