In the 1970s, legendary rock musician Danny Collins (Al Pacino) was experiencing a low point in his life. His agent (Christopher Plummer) discovered a letter that had never been delivered in 40 years. This letter turned out to be from the Beatles lead singer John Lennon who wrote to him when he was 19 years old 40 years ago. This inspired him again and he resolutely left his current luxurious life and embarked on a journey to find the meaning of life. During this journey, he also gained true love and long-lost creative inspiration.