C-

The widely-circulated trailer to “Man on a Ledge” is one of the worst recent examples of an advertisement that gives away entirely too much about the plot. To be sure, the big “surprise” in Pablo F. Fenjves’ script comes pretty early, but the movie might work better if it weren’t revealed in the previews that the titular fellow’s supposed threat of public suicide is only a gambit designed to deflect attention from a heist. (Remember, a reviewer can’t be castigated for spoiling a plot twist the company’s already revealed.)

Anyway, the fellow in question is Nick Cassidy (Sam Worthington), who waltzes into a New York City hotel, takes a room with street view, orders a big breakfast, and then climbs out the window, immediately attracting the attention of cops, onlookers and, of course, the sensationalist press (represented by Kyra Sedgwick as gossipy TV reporter quickly being broadcast live from the scene). It’s not long before police negotiator Lydia Mercer (Elizabeth Banks) is called in to try to talk him down, taking over from her brusque regular Joe colleague Jack Dougherty (Ed Burns).

But Nick is no ordinary jumper, we soon learn. He’s an ex-cop who’d been convicted of stealing a diamond from ruthless real-estate mogul David Englander (Ed Harris), whose offices—and vault—just happen to be down the block. Nick had recently escaped prison during an outing to attend his father’s funeral, and now his ploy is a diversion that will allow his brother Joey (Jamie Bell) and Joey’s girlfriend Angie (Genesis Rodriguez) to break into Englander’s Fort Knox-like inner sanctum and take the rock to prove that the supposed theft was nothing more than an insurance scam to get the magnate the cash he needed to stay afloat during the recession.

So “Man on a Ledge” morphs into a bipartite thriller that alternates between the Nick-Lydia scenes (over the course of which, naturally, she begins to believe in his innocence) and the robbery undertaken by Joey and Angie, which possesses a degree of physical agility and high-tech wizardry one would imagine to be beyond the skill of a couple of schlubs from the neighborhood. An added layer of supposed suspense is added to the mix by the ambiguous role of Mike Ackerman (Anthony Mackie), Nick’s old partner, who seems to be a friend but…well, you know.

The basic problem with the picture is that it quickly loses any sense of credibility, devolving into near-farcical implausibility. The “Mission Impossible” character of the robbery perpetrated by Joey and Angie is just the tip of the iceberg. You also have to accept that nobody—least of all Mercer—ever notices that Cassidy is wearing an earpiece and occasionally chatting with his confederates from the ledge. And the big twist at the close—involving the hotel busboy who takes Nick to his room, played by Bill Sadler—may be satisfying in typical Hollywood fashion, but makes the whole first act ludicrous.

Setting all that aside, however, one’s left with execution that’s mediocre. Asger Leth’s direction comes alive during some of the action moments, but elsewhere it’s pretty lax, which is fatal in this kind of picture. And he doesn’t deal well with his cast. Worthington makes a bland hero, and Banks a flat counterpoint to him. And though Bell and Rodriguez have some fun in what are basically comic-relief parts and Sedgwick offers a few minutes of welcome satirical bite, Mackie’s totally wasted, while Harris is allowed to get away with such astronomical scenery-chewing as the ruthless tycoon that he really ought to have been fitted with a moustache to twirl. The best barometer of audience response, though, is certainly Burns, who sleepwalks through his role with such ennui that one supposes he was merely impatiently waiting to get the paycheck he might then plow into his next directorial effort. Adequate technical credits, including a score by Henry Jackman that tries desperately to pump up the excitement, complete the unhappy picture.

Things get so bad at points during “Man on a Ledge” that you might be inclined to join the more nasty elements among the sidewalk onlookers and shout “Jump already!” It turns out that in the end Nick does take a dive from the building—in a fashion that, in a movie already rife with implausibility, takes it straight into the realm of the completely absurd. That’s not a spoiler; it’s simple fact.