The seventies were the great age of the paranoid political thriller, and recent attempts to revive it have proven pretty pallid. On the evidence of the present picture, even Roman Polanski, who was able to employ his plain, overtly naturalistic style to genuinely creepy effect in “Rosemary’s Baby,” isn’t the person to resuscitate it. Like “Frantic,” his 1988 attempt to emulate “The Man Who Knew Too Much,” his adaptation of Robert Harris’ 2007 novel is—if you’ll pardon the pun—like a ghost of the sort of film he’s aiming for.

Essentially the plot is a variant of John le Carre’s “Tinker, Tailor, Soldier, Spy,” which fictionalized the story of Kim Philby, the British intelligence bigwig who became a double agent for the KGB. What Harris did was to update the idea to the present, and transfer it from the intelligence to the political world. And, in this era of War on Terror as opposed to Cold War, the controlling power becomes not the Russkies but the Americans, who use a British prime minister as the instrument of their agenda in the Middle East.

The PM in question is Adam Lang (Pierce Brosnan), an obvious stand-in for Tony Blair, who’s retired from government and writing his memoirs. Unfortunately, the body of his ghost writer has washed up on the Massachusetts beach where Lang and his entourage are holed up in his publisher’s house—either a suicide or accidental drowning victim, it appears—and they’re in desperate need of a replacement if the imminent deadline is to be met. That leads to the speedy employment of a new, unnamed ghost (Ewan McGregor) after what appears perfunctory vetting by Lang’s lawyer (Timothy Hutton) and his abrasive Yank publisher (James Belushi).

Before long our hero has been transported to Lang’s Massachusetts compound, where he finds the manuscript a hopeless mess and the household stressed by the obvious antagonism between the politician’s bitter wife Ruth (Olivia Williams) and his ever-efficient, constantly hovering secretary Amelia (Kim Cattrall). To make matters worse, news reports indicate that Lang is about to be indicted by the International Criminal Court on charges he turned over four British citizens of Middle Eastern descent to the U.S. for some of Dick Cheney’s enhanced interrogation techniques, during which one of them died—charges supported by his onetime foreign minister (Robert Pugh). That brings a raft of demonstrators, as well as journalists, to town, among them a furious Brit whose son was killed in the Iraq war—a death for which he blames Lang, who was submissive to American policy.

All that, however, is secondary to the real “thriller” meat of the plot—the writer’s increasing suspicion that his dead predecessor discovered something explosive in Lang’s past and was killed to keep him quiet. He spends so much time tracking down leads—and bedding the unhappy Ruth one night—that you have to wonder how he gets any rewriting done at all. Still, his investigations do offer two of the best moments in the picture—a cameo by veteran Eli Wallach as a crusty old guy who lives near the beach and insists that the first ghost’s death couldn’t have been an accident, and a longer scene in which the writer meets with Paul Emmett (Tom Wilkinson), an enigmatic, and more than slightly menacing, Harvard professor who’s clearly trying the conceal his friendship with Lang during the Brit’s carefree days at Cambridge.

Apart from those sequences—and the performances for Williams, whose intensity as Ruth is almost frightening, and Belushi, who’s offhandedly blustery (as well as that of Tim Preece, as a flustered editor)—“The Ghost Writer” is surprisingly nondescript. Polanski’s direction is more workmanlike than inspired—even a chase sequence involving a ferry, which should have been pulse-pounding, is anemic, and his attempt at a Hitchcockian pan at the close, in which a slip of paper is passed from hand to hand to reach its intended recipient, is too muddily staged to have much impact. It’s then capped by a reversal that’s a sort of contemporary reworking of the pessimistic close of “The Parallax View,” still the class of the genre. It’s interestingly shot, but ultimately undone by the fact that McGregor is so wan that he never manages to get us to identify with him. In effect he’s replacing Alec Guinness’ George Smiley from the “Tinker” mini-series, but he’s about as successful at it as he was taking over Obi Wan Kenobi from the older actor in the second “Star Wars” trilogy—which is to say not very.

The weakness of the picture is accentuated by the fact that the European locations never really resemble the Massachusetts setting, despite the best efforts of production designer Albrecht Konrad and art directors David Scheunemann, Cornelia Ott and Steve Summersgill. And Pawel Edelman’s cinematography, like Polanski’s direction, is plain to the point of dullness. On the other hand, Alexandre Desplat’s score is more interesting than his other recent work, adding some welcome giddiness to some scenes and propulsion to others. Long stretches pass without music, though.

But ultimately what undoes the movie is that when the ultimate revelation comes, the average viewer’s reaction may well be, “That’s it? That’s what corpses have been piling up over?” From a British perspective, the skewering of Tony Blair—who’s terribly unpopular now—will be as delightful as the manhandling of Richard Nixon has been for American audiences, from “All the President’s Men” to “Frost/Nixon.” And their rich tradition of Philbyesque turncoats will give the denouement a degree of resonance it lacks for Yanks, who will probably think it all amounts to a tempest in an English teacup. Like the spirits the title refers to, Polanski’s picture seems pale, weightless—and compared to the best paranoid thrillers—surprisingly ephemeral.