Perhaps “Mr. Pitt and Ms. Jolie” would have been a more appropriate title for this film, because without the magnitude of these actors’ star appeal and abilities to appear likeable even as cold-blooded killers, this movie would be a sure dud.

With shaky direction, an implausible script and characters which seem to be molded to fit each scene, it’s a good thing Brad Pitt (Mr. Smith) and Angelina Jolie (Mrs. Smith) have such sparkling charisma and their chemistry, under intense public scrutiny offscreen, is just as alluring on film.

“Mr. and Mrs. Smith” is a story of two rival assassins who have been married for “five or six” years, all the while ignorant of each other’s true identities. When the pair ends up assigned to make the same hit, their secret lives are revealed and they end up trying to kill each other instead.

Most of the comedy lies in the preposterousness of the couple’s situation, opening the door for a lighthearted stream of action and terribly campy humor. “Your aim’s just as bad as your cooking, honey,” says Pitt nonchalantly as he dodges bullets from Jolie. This none too serious approach works at first and even in the midst of their combat, we seem to forget the couple are, in fact, murderers. Their initial affection is so charming and their personal vulnerability is so convincing, one wishes they’d just stop trying to kill each other and make up.

But director Doug Liman seems to stop the comical tone halfway through the movie, choosing instead to focus on the seriousness of the couple’s emotions and the danger they both face from outside forces. The plot takes an interesting turn, but the slightly self-mocking approach turns into a full-fledged “us against them” drama, complete with slow-motion scenes of Pitt and Jolie shooting and dodging bullets together.

Because the foundation for the movie lacks any believability, the ultra dramatic finale seems a tad ridiculous and the overall message becomes confusing.

Altogether, “Smith” is entertaining, but without the charm of its two leads, it’s more like a really long, bad joke.