With all the market research and focus groups that drive the movie world, it's rare for something as poorly conceived as "The Son" to make it through the cracks.

Florian Zeller's bleak follow-up to his Oscar-winning "The Father" is only loosely connected to that movie, both in terms of story and quality. The title could refer to either Peter (Hugh Jackman), a crack political strategist, or his troubled child Nicholas (Zen McGrath), who lives with his mother, Kate (Laura Dern), and has not adjusted well to his parents' divorce or his dad's remarriage to Beth (Vanessa Kirby).

Early in "The Son," Nicholas announces that he'd rather live with his father, a sign that all is not well in this amicably divorced, Restoration Hardware world. In short order, there are problems at school and at home and a doctor, who has placed Nicholas in residential care for his depression and other issues, is breaking the news to Peter and Kate that they must take their son's health seriously.

That's where "The Son" goes off the rails. It's an interesting idea for Zeller to depict Peter and Kate as unable to separate Nicholas' health from their parenting successes and failures, but the script begins to make no sense as they react to their son's difficulties.

It defies belief, for instance, that they would keep loaded guns in their homes or that a family that lives with privilege and comfort in the therapist-rich heart of Manhattan would have no knowledge of mental health issues. This becomes even less credible when Peter's father appears, late in the movie. It's not just that they aren't certain how to deal with depression, but that they seem never to have heard of it.

As in "The Father," Zeller has a gift for capturing the details of troubled domesticity. The shifting relationships are compelling, particularly the one between Nicholas and his stepmother, which seems to have the most potential because it is the least clearly delineated. There's also something truthful about the way Nicholas' parents, who feel helpless, both hope the other has a better answer than their own.

Zeller still does good work with actors, particularly Jackman and McGrath. But just about everything that happens in "The Son" once Nicholas receives his diagnosis is not just hard to swallow but also irresponsible. The movie has nothing to say about mental illness, other than to exploit it to generate suspense, as in "What terrible event is going to happen next as a result of the parents' blindness?"

That's probably the worst of the many bad things in "The Son." It never really cares about what's happening with Nicholas, only framing his health issues in terms of their impact on the adults in his life.

In the end, I suppose that means Jackman is playing the title character. But it doesn't matter. Whether it's Jackman or McGrath, the movie completely fails them.

'The Son'

0 out of 4 stars

Rated: PG-13, for language and dark subject matter.

Where: In theaters Friday.