‘The Good Liar’ review: Helen Mirren and Ian McKellen are transfixing

If Helen Mirren‘s and Ian McKellen‘s characters in “The Good Liar” were Catholic, they’d have to book a week’s stay in a confessional.

Take Betty and Roy’s first meeting, at a posh London restaurant. Having connected through a dating website for seniors, they introduce themselves as Estelle and Brian. Lies! Wait — Betty said on her profile she doesn’t drink. So, why is there a martini in her hand? It’s clear we can’t buy a word either says.

A taut thriller, “The Good Liar” keeps you guessing ’til its explosive end. Director Bill Condon’s film is based on the novel by Nicholas Searle, and builds much in the same way a book does. You gotta get through the first 30 pages to become fully absorbed.

What brings Betty and Roy to a second date, and a third, after their initial breach of trust would seem to be their age. Both are widowed (possibly), and it’s tough finding companionship at any time, let alone in your 70s and 80s. That deep need lends this wild tale of snowballing falsehoods some much-needed believability.

Roy isn’t just telling little white lies, by the way. He’s actually a con man attempting to swindle Betty out of millions of pounds by having her transfer the money into his account to make a bogus investment. She falls for his song and dance, no doubt thinking Roy is more of a Gandalf than a Magneto. How naive. (Possibly?)

Roy even fakes a knee injury to squeeze his way into her suburban home. Her skeptical grandson (Russell Tovey) sees him as an opportunistic invader. Regardless, Betty and Roy jet off on a holiday to Berlin, where Betty finally swallows some bitte truths. (I think?)

The fun of “The Good Liar” is that, just when you think you’ve got a proper handle on what’s going on, your reality is completely shattered. A few times. And while the film is a thriller, Mirren and McKellen are nimble enough to keep things as bouncy as a Noël Coward play.

And what a pleasure it is to see two such giants going head to head. They manage to be both warm and scary, and it’s hard to imagine this film working without them. It’s big, dangerous acting in the tradition of “Brief Encounter.”

Their invisible co-star is Carter Burwell’s menacing score. The composer doesn’t get talked about as much as his showier peers, but he wrote one of the finest film scores of the decade, for 2015’s “Carol.” More so than any screen composer today, Burwell understands that music is there to express what cannot be said. And in a web of lies, that’s a lot.