As titles go, “Man on a Ledge” gives fair warning of its subject matter: We’ve got a dude standing outside the window of a high-rise, and a bunch of people are trying to talk him down.

The dude is Nick (“Avatar” man Sam Worthington), an ex-cop with a bone to pick. He’s standing out on the ledge of a hotel, while inside the room an NYPD detective (Edward Burns) and police psychologist (Elizabeth Banks) talk to him.

At first, they’re trying to get him back inside the room. Then they suspect something else entirely might be going on here.

Best not to detail that story, although it involves Nick’s brother (Jamie Bell) and the brother’s girlfriend (Genesis Rodriguez, who, by the way, lives up to her name). They are pulling off a task while Nick distracts the attention of the neighborhood.

There’s also a bit of backstory involving the mayor (Ed Harris, weathered and furious) and various levels of revenge. All of which becomes increasingly hard to believe as the movie goes on.

The thing that most hurts the film (or helps it, depending on how seriously you want to take any of this) is the tone. For some reason, screenwriter Pablo F. Fenjves and director Asgard Leth have decided to play all this as a breezy, knockabout action comedy; I almost expected Mel Gibson and Danny Glover to come charging in, guns drawn, to throw a few one-liners around.

This works all right when Jamie Bell (a versatile actor lately seen beneath the animation of “The Adventures of Tintin”) and Rodriguez are on screen. Their unlikely pairing is already amusing, and their characters are suited to bumbling along.

But that kind of patter continues even in the most perilous moments for Nick, whose perch outside is hardly secure, after all. Granted, this cynical-comic approach can work, but if the movie also wants us to take seriously some of the issues of betrayal and punishment that it brings up, perhaps it’s best not to get all lightweight on us in the process.

If the movie in general is off-key, at least it can’t be accused of taking itself too seriously. By the time Nick takes his, ah, final plunge, you’ve either gone along with this nonsense or you’ve gotten up to see what’s playing in the theater next door. Either way is an acceptable response to “Man on a Ledge.”

“Man on a Ledge”

An ex-cop (Sam Worthington) is indeed out there on the ledge of a high-rise hotel, while various levels of intrigue swirl beneath him. This implausible movie takes a breezy, comical approach to its apparently serious subject matter, which is only one reason it doesn’t truly click.

Rated: PG-13 for violence, language.

Showing: Alderwood Mall, Everett Stadium, Galaxy Monroe, Marysville, Stanwood, Meridian, Metro, Cascade Mall