'Philomena' is elevated by actors Judi Dench and Steve Coogan

'Philomena' stars Dench as a woman searching for the son she gave up for adoption and Coogan as the journalist writing a story about her.

The first thing you have to overcome while watching “Philomena” is the spectacle of Judi Dench playing a quietly reserved Irish woman who laps up trashy romance novels and gets her kicks watching “Big Momma’s House.”

But have no fear: Dench is such a consummate actress that Philomena’s proclivities soon appear perfectly natural. Just because Dench is great at playing smart doesn’t mean she can’t also play not-so-smart. As a matter of fact, the actress’s intelligence in this regard is probably an asset. (Judy Holliday, the quintessential dumb blonde of “Born Yesterday,” was reportedly a brainiac). Actually, Philomena Lee, although the movie sometimes confers upon her a slight condescension, isn’t all that stupid, just incurious. She lives a homespun, circumscribed life – except for one thing. Fifty years earlier, after becoming pregnant following a youthful indiscretion, she was forced by her parents into a convent, where she was worked like a packhorse and allowed to see her baby boy for just one hour each day. Three years later the baby was sold to an American couple, and forever after not a day has gone by without Philomena wondering what became of him.

Her daughter, upon learning of this long-held secret, reaches out to Martin Sixsmith (Steve Coogan), a former BBC reporter and government spokesman (i.e., spin doctor) who sees Philomena’s story as his human-interest ticket back into journalism.

Based on Sixsmith’s 2009 nonfiction book, “The Lost Child of Philomena Lee,” and directed by Stephen Frears, “Philomena” is a straightforward recounting of how this odd couple journeyed from Ireland to Washington, D.C., and then back to Ireland in search of answers.

Coogan, who co-wrote the script with Jeff Pope, sets up these people as polar opposites: She’s a God-fearing Roman Catholic who, despite what was perpetrated by the convent, holds no malice. She simply wants to know about her son. Martin, by contrast, is a devout atheist who is enraged by what happened to her and can’t sanction her forgiveness.

This is all rather schematic. At times the filmmakers seem to be taking potshots at Philomena for her placidity; other times Martin is made to seem crass and unfeeling – insufficiently spiritual. Life lessons are imparted, although the players never budge very much from their initial attitudes.

The search for the son, as it slowly ensues, is gripping, and leads into byways one would not expect. The road movie becomes a detective story that opens up a fresh wound even as it closes another. Frears doesn’t make a big show out of any of this. He holds back from the big tear-jerky moments that a lesser director would have hit home.

But there’s also an old-fashioned aspect to his work here that is a bit dozy. If not for the expertness of his actors, “Philomena” would be a sloggy journey indeed. Fortunately, Dench and Coogan are more than capable of turning water into wine. Grade: B (Rated PG-13 for some language.)