Singing and winking all the way

Like all good scams, "Dirty Rotten Scoundrels" keeps you guessing right up until the end. Is it a smart, brassy sendup of musical conventions, full of naughty byplay, or a cynical reworking of those conventions, with a few vulgarities tossed in to make it seem hip?

The musical, which opened last night at the Opera House, follows the story of the movie it's based on, about two con men plying their trade on the French Riviera: suave Lawrence and crude Freddy, each with a few tricks up his sleeve. They soon realize they'll have better luck with the rich tourist ladies who are their marks if they work together. Then Christine Colgate, the "American Soap Queen," shows up, and soon Freddy and Lawrence are playing thehighest-stakes game of their lives.

Well, that's plenty of plot to start with, and Jeffrey Lane's book keeps it twisting along nicely from there, right up to the satisfying (but hardly startling) switcheroo near the end. David Yazbek's songs have some lively twists, too, with plenty of slinky melodies to match the slithering maneuvers of the con men and a few amusing showstoppers that at once mimic and mock such standbys as the inspiring love anthem and the rollickin' cowboy chorus number. Meanwhile, Lane has the characters breaking through the fourth wall to address the conductor, the audience, even a lovestruck usher.

That's all in keeping with the self-mocking, self-regarding tone of the whole piece. Sometimes it's fun; sometimes, like the clever and mock-grandiose sets by David Rockwell, it's just a little too pleased with itself. It can feel like a scam in which you're being told that it's a scam, but you're still expected to hand over the cash. And it can also feel as if you're being asked to fall in love with an old-fashioned musical -- then mocked for not being wise to the old-fashioned games.

You can see how John Lithgow ended up playing Lawrence on Broadway; the part, like the play, demands exactly his mix of smarts and smugness. And it will probably appeal most to those who share the insider-y glee of being in on a con, rather than being dispirited by its easy cynicism.

If Tom Hewitt's Lawrence sometimes seems to be channeling Harvey Korman more than Lithgow, he still sets the tone for the generally strong touring cast. His line readings, like those of D.B. Bonds's Freddy and Kim Shriver as a wealthy pigeon, are as broad as a barn, but that seems to be what's required. And Northampton native Laura Marie Duncan brightens the stage every time she enters, both with a lovely voice and with a lively, playful rendering of the mischievous Christine.

So is it a winning ticket or a wooden nickel? You may have to see for yourself. But keep one hand on your wallet.

Louise Kennedy can be reached at kennedy@globe.com.