Bill Condon’s The Good Liar gathers British acting royalty, but is not a crowning achievement compared to the career highlights of the principals involved. We have Sir Ian McKellen and Dame Helen Mirren in a twisty con artist tale based on a Nicholas Searle novel.

The film tests the limits of whether having these two leads is good enough. For a decent portion of the running time, the answer is yes. McKellen is Roy Courtnay, who successfully bilks investors out of millions along with partner Vincent (Jim Carter). His latest conquest is The Rich Widow Con and that’s Mirren’s Betty McLeish. Roy’s got patience when it comes to lifting her bank account. He attempts to ingratiate himself to her only grandson (Russell Tovey). Roy soon moves into Betty’s drab home. Past victims of his grifts are on his trail. And there’s a bit of mystery whether their partnership will move beyond platonic.

In its first half, The Good Liar is a concoction as bubbly as the wine Betty enjoys during their first date after meeting online. It is a humorous opening credits touch as they chat on the computer. Roy checks the box for non-smoker as he puffs away on a cigarette. Betty claims not to be a drinker with glass in hand. With these two master thespians bouncing dialogue off one another, it’s often a treat. On the other hand, we aren’t seeing anything unseen in the genre before with the exception of the age of the performers involved.

When flashbacks to Roy and Betty’s pasts come into play later, the pic loses its frothy charms and becomes far more serious and considerably more absurd at the same time. I am not confident that the plot mechanisms that rocket into overdrive in the latter portion hold up on close inspection. It’s telling that some of the reveals aren’t worth racking the brain about. There’s no doubt that McKellen and Mirren’s interplay is fun for awhile. When their story ventures into more weighty subjects, it doesn’t feel earned delving into them.

**1/2 (out of four)