After a few years, many marriages start to get in a rut. Mr. & Mrs. Smith starts with a couple in marriage counseling after five or six years together — they can't even agree on how long. On the surface they lead typical suburban lives in which the main concerns seem apparently dinner and decorating.

But that is all just a front. John (Brad Pitt) and Jane Smith (Angelina Jolie) are both expert assassins working for rival companies. Neither knows about the other's secret life.

Pitt and Jolie play well together, and the rapport they have onscreen is the best asset of this otherwise overblown action comedy. The therapy sessions work to fill in the background of the Smiths' marriage, including their cute first meeting after an assassination in South America.

In all their years together, neither of these highly professional assassins has discovered any clues about the other's activities. Both have stashes of high-powered weapons in their suburban house. Both go out to work at odd hours, trying to fit hits in between their cover jobs and evening dinner parties with the boring neighbors.

To cover up how weird this all is, it's staged for absurdity. Jane switches into a dominatrix outfit for one job, barely escapes alive, and rushes back home to be in time for the party, where she suddenly realizes she still has rather racy stockings on.

The companies they work for are not explained too clearly. Jane's company seems to be a mostly all-female affair with glamorous killers. John's is a more laid-back business fronted by a phony construction company. Who the clients and victims are is completely glossed over. The companies are just a fictional conceit to be able to have the marriage-troubled couple shooting at each other, which is, of course, the whole concept behind the film. Typical marital spats are escalated to the level of maximum destruction.

After a brief setup, the inevitable happens: The Smiths wind up in each other's gun sights. The two of them are sent separately to a remote area in a desert, but it's just a trap. After all this time, their employers have figured out that they're married and consider it an unacceptable risk. The rival assassination companies embark on a rare joint venture to clean house, hoping the two will wipe each other out.

They survive, though. Jane pretty much figures out who was shooting at her. John doesn't get a good look but has a few clues. It soon turns into a cat-and-mouse game of equally matched opponents. At first, it is pretty amusing. They pretend not to know and wait to take advantage of any false move. Then they take a more serious approach involving bombs, surveillance cameras, zip lines and high-tech weaponry.

There is a clever moment when John criticizes Jane's recent choice of new curtains while shooting at her. The film needed to take that tone more often. Anyone who was once married will understand how these little domestic details still anger the couple even after they start the serious shooting.

The film then goes for the bigger-is-better approach, with every scene larger and noisier than the preceding one. By the end, it's gone on for about half an hour too long, and almost all of that can be accounted for by the unnecessary special effects.

The film really does belong to Pitt and Jolie, whose characters seem to love and at the same time love to hate each other. The only supporting character worth mentioning is Vince Vaughn, who plays a colleague of John's. In another underdeveloped idea in the script, Vaughn is an assassin who still lives at home with his mother. He has been pretty busy recently in sidekick roles, and is starting to master them.