The drug epidemic sweeping America presently is affecting millions of people who in the past might have been untouched by the devastation of illegal narcotics and abused prescription medications. The new movie “Beautiful Boy” offers an occasionally harrowing reminder of that sad and scary fact while offering a touching real-life Prodigal Son story in which an ever-patient father never stops loving his son.

Starring Steve Carell as veteran journalist David Sheff and rising French actor Timothee Chalamet as his troubled teenage son Nic, “Boy” is based on an unusual pair of best-selling memoirs written by the pair. David wrote the book “Beautiful Boy” to recount his experiences trying to save his son from a father’s point of view, while Nic wrote “Tweak” from the point of view of an addict mired in personal torment who has to learn to accept his father’s love.

The casting of Carell, currently one of our best screen everyman characters, as David makes his dilemma instantly relatable. He opens the film speaking to a drug expert, desperate for answers about the odds of recovery for his son, and about the damage that an addiction to crystal meth can do to the human brain.

The answers aren’t pretty. Soon the film jumps back a year, when David first notices that Nic has become a surly, oversleeping mess who’s starting to lose all of his ambition. Nic had been eager to follow in David’s footsteps as a career writer as well as an illustrator, but now he’s simply chasing the next high from an array of drugs including marijuana, cocaine, ecstasy and heroin, with meth his secret worst drug of all.

David and Nic’s mother Vicki (Amy Ryan) split up when Nic was a pre-schooler, subjecting him to a confusing childhood in which he spent summers and holidays with his mom in Los Angeles and the rest of the year with David. David also has second wife Karen (Maura Tierney) and two new young children to contend with. While he tried to give Nic everything he thought he needed as a child, a stirring series of flashbacks throughout starts to show David the cracks in the façade of happiness during Nic’s adolescence.

David forces Nic into a 28-day rehab that appears to be effective at first. But when Nic escapes a follow-up stay in a halfway house and winds up vomiting in an alley in another city, he realizes that he’s got a monster of a problem on his hands — one he has to navigate carefully not only so that he doesn’t lose Nic, but doesn’t cause the relationships with his new family to suffer.

“Beautiful Boy” takes its name from a John Lennon ode to his younger son Sean that appeared on the album “Double Fantasy,” released right before his assassination. David sings it to Nic as a young child in one of the film’s most touching moments, and director Felix van Groeningen (who co-wrote the screenplay with Luke Davies) effectively takes viewers through the ever-unpredictable world of ping-ponging emotions and crises that envelop any family dealing with a serious addiction. Carell and Chalamet are terrific in their roles, with Chalamet a constantly shifting emotional chameleon.

While the message of “Beautiful Boy” is a touching portrait of familial love, forgiveness and reconciliation, the constant merry-go-round that Nic subjects his family to eventually begins to grate. He may have been shuttled between parents, but every indication also showed that they each doted on him during their turns with custody.

Thus, it never becomes fully clear why Nic became such a seeker of trouble for himself and others; rather, he merely says the day-to-day of life is hard and of little interest to him, and thus feels entitled to spice it up with chaos. By the final half hour, viewers will likely want to join David in screaming at him to get it together.

One thing that does seem apparent, whether the filmmakers intended it to be so, is that Nic has been raised without a sense of purpose. Before realizing that his son has a drug problem, David laughs while recounting the fact that he experimented with an array of illegal drugs during his own younger days, and even shares a joint with Nic.

If anything, this film seems to be showing the ennui that can set in when one just lets existence pass by. “Beautiful Boy” should serve as a cautionary tale to parents not to assume that their teens are alright, but to give them a sense of morality and ethics if they hope to instill a truly happy and grounded life in them.   

“Beautiful Boy” Grade: B