What is the full name of the person that decides to change their life after reading a 40 year old letter?
Aging 1970s rocker Danny Collins cannot give up his hard-living ways – but then his manager, Frank Grubman, uncovers a 40-year-old undelivered letter to him from John Lennon. After reading the letter, Danny decides to change his way of life. He travels to New Jersey to attempt to connect for the first time with his grown son, Tom Donnelly, whom he sired from a casual relationship with a woman who died 10 years before. Tom has a wife, Samantha and seven-year old daughter, Hope.
Seeking a new start, Danny forswears touring and checks into a Hilton hotel in New Jersey, much to the delight of the young staff. He begins to woo the hotel manager, Mary. 
Tom initially rejects the father he believes abandoned him, but Danny persists, getting Hope, who has ADHD, into an exclusive school for children with special needs. He learns Tom has what doctors say may be terminal leukemia, inherited from his mother, and begins to attend doctor's visits with him. Tom's dislike of his father gradually gives way to the need for his support.
Inspired by his feelings for Mary and his happiness at having a family, Danny begins to write new songs. He books a one-night performance at a small club. When the audience demands he play his old material, however, Danny loses his nerve and gives a rote performance. Ashamed, he resumes doing drugs, damaging his relationship with Mary and his family. Tom confronts him, causing Danny to angrily reveal Tom's leukemia diagnosis, something Samantha had not been aware of. Tom, feeling betrayed, tells Danny never to bother his family again.
Danny Collins