"East London is a vampire/ It sucks the joy right out of me," snaps Kele Okereke on "Song for Clay (Disappear Here)," the opener to Bloc Party's second LP, A Weekend in the City.

The urgent inflection of these words seems to frenetically shepherd in what can only be called a statement album. Spurred on by razor-sharp, angular riffs, "Clay" progresses with white heat and shrouds the horizon with seeming glimpses of kinetic outrage. Here's a zealous, politically charged knockout just waiting to unfold.

Yet a full tour of A Weekend in the City does not bring this statement to fruition. Instead, it will leave listeners annoyed and bored.

How is this possible? How could its early spurts of fire-starting fervor end up as anomalies on a drab, navel-gazing non-starter? This is Bloc Party we're talking about, the thinking man's Franz Ferdinand, whose 2005 debut Silent Alarm abounded in taut, wine-dark kineticism and nervous art-rock shudders. A Weekend in the City reprises the general aesthetic of its predecessor, but goes crosswise in its delivery. These are trapped sounds of plodding passion and competent songcraft that too rarely erupt into vibrant form.

Sadly, this foreknowledge will dampen the satisfaction of A Weekend's sparse highlights and induce frustration with its aberrational thrills. "Song for Clay (Disappear Here)" really is a propulsive, kick-ass thrasher (despite its liberal appropriation of a guitar line from Franz's "Jacqueline"). Its superbly tense momentum, carried through by fidgety percussion and crackling guitar slashes, proceeds in the spirit of Silent Alarm while upping the ante with its bleak commentary. Unlike much of this effort, "Clay" clearly is working toward an apex with all of its cylinders chugging. The politically heated follower "Hunting for Witches" pounds in a similar manner, and the stomping single "The Prayer" rounds out the high-end stuff.

"Uniform" initiates the painful, six-song slide that captures the true motif of A Weekend in the City. Prior to its release, Okereke promised themes of anger and bewilderment would dominate the band's sophomore effort. The album was to be a newly matured modernite's exposition on detachment, loss, identity and paranoia in 21st-century London.

But, truth be told, Okereke's more sap than cynic and somehow manages to drain his emotional longings of their color and vitality. On "Uniform," he croons, "The TV taught me how to sulk and love nothing," a line of staggeringly sophomoric pop psychology. This is not resonant. It's enervating, in the sense of the word that Ben Affleck meant when he used it to describe the uninspiring demeanor of John Kerry.

The ponderous affair crawls along with "On," "Kreuzberg" and "I Still Remember," which overflows with bland imagery: "And our love could have soared over playgrounds and rooftops." When vocalized, Okereke's lyricism often comes off forced and labored as he awkwardly stretches out syllables to match the pacing of the music.

These shortcomings would not stand in such sharp relief if the adjoining instrumental sounds were more dynamic. Okereke's vocals need the tension of knifing guitar work to reach a natural stride. But the sonic patterns of the entire second half are stuck in a monochrome delivery, as initially subdued noises give way to predictable guitar swells.

This always develops in a belated manner, and the choruses are too clean, unimaginative and contrived to invigorate the fading appeal.

"Sunday" struggles with this. It concludes with empty power chords that scarily resemble missteps from the Killers' bruising 2006 disappointment Sam's Town. As this song demonstrates, an abrupt surge of scratchy riffs cannot resurrect each pensive track with a minute and a half outro. It's already doomed by this point, as much of this album certainly appears to be.

A Weekend in the City is not a precipitous tumble for Bloc Party, nor is it any sort of radical miscalculation. No one should utter "Oh, how the mighty fall" in regard to this work. But it is not a success either. Bloc Party has curiously strayed from the winning elements of Silent Alarm's repertoire, even while retaining its basic sound. It generally goes for speed but rarely settles into a galloping pace. Its guitar work strives for peaks but often hides away until the final takeoff.

Rather than crisp and sweaty, the album is overly polished and inhibited. This translates into the most troubling fault of A Weekend in the City: It's still art rock, but this time around, it's barely danceable.

Grade: two-and-a-half out of five.