Movie stories often begin with the hero or heroine having everything and then losing it or having nothing and then finding it. But some of the best combine them both, as Writer/director Dan Fogelman (“Cars,” “Tangled,” “Crazy Stupid Love”) has with “Danny Collins,” a heartwarming story of a one time rock star (Al Pacino) who can fill a stadium with his baby boomer fans but has an empty life that even a hot young fiancee and constant partying cannot hide.

And then he discovers that 40 years ago, when he admitted in an interview that he was afraid of becoming successful because it might impair his integrity as an artist, John Lennon sent him a letter saying that it did not have to happen that way and encouraging him to call. The letter never reached him until four decades later, when Collins’ longtime manager and best friend (Christopher Plummer) found it from a collector and bought it as a surprise birthday gift. (This part of the story is inspired by a real-life musician in the UK who did find out 34 years after it was written that John Lennon had sent him a letter almost identical to the one in the film, as we see in the closing credits.)

The letter serves as a wake-up call, instantly connecting Danny to the musician he once was. He cancels his tour, breaks up with the fiancee, and orders his private plane to New Jersey, where he moves into a suburban hotel managed by Mary (a deliciously crisp Annette Bening). He buys a new piano and has it delivered to his hotel room so he can start composing. And he reaches out to the son he has never met (Bobby Cannavale), who lives in New Jersey with his pregnant wife (Jennifer Garner) and young daughter (the delightful Giselle Eisenberg).

It is a treat to see the flamboyant rock star being checked into the numbingly generic hotel by an agog college student (Melissa Benoist of “Whiplash” and the Supergirl TV series) as stunning a transition for him as if he was Alice through the Looking Glass. Pacino is not entirely convincing as a rock star on stage but his genially raffish charm is as endearing to us as it is to the civilians he charms along the way. The highlight of the film is what he calls his “patter” with Mary, a sparkling throwback to the kind of romantic banter that might have been tossed back and forth by Tracy and Hepburn.

Immune to his charm, at least at first, is his son, even after Danny performs some rock star magic to help the family. But that’s what movies are for — to let us see Danny overcome his son’s efforts not to give in, all to the tune of some of Lennon’s most moving songs. And to wonder what we might do differently if we got a long-lost letter from Lennon.

Note: Danny’s catchy song, “Hey Baby Doll” was written by INXS replacement frontman Ciaran Gribbin, selected in a competition with top Hollywood songwriters for a tune that could sound like a real hit from the 60’s.

Parents should know that this film includes rock star behavior including sexual references and nudity, drinking and drug use, and very strong language, as well as family issues including abandonment and illness.

Family discussion: Who would you most like to get a letter from and what would you want it to say? Why did getting the letter make Danny decide to change his life? How often do get to enjoy patter?

If you like this, try: “One Trick Pony” and “The Last Waltz”