Midway through Roman Polanski’s new thriller The Ghost Writer, the wife of a former British Prime Minister compares the couple’s extended stay at a supporter’s compound on Martha’s Vineyard to Napoleon’s exile on St. Helena. If this elegantly plodding picture, which Polanski co-wrote with novelist Robert Harris, is the fugitive director’s volley at America for his treatment at the hands of our legal system, then he’s firing blanks. Certainly the imperial analogy is generous: A cinematic Napoleon might have directed Rosemary’s Baby, Chinatown, and The Pianist, yet too often the filmmaker behind this effort appears to be a shadow of his former self and rarely a major screen threat.

I hasten to add, the fault lies mostly with the plot and The Ghost Writer is more sophisticated and accomplished than the majority of movies unspooling at the multiplex. Polanski’s mordant sense of humor and knack for creating a tense atmosphere are very much in evidence --  the latter effect abetted by composer Alexandre Desplat’s score. While there are tantalizing hints of Polanski’s genius, however, the overriding sense is that this is the work of a director scrambling to stay relevant, of a talent suffering from cabin fever and anxious not to seem out of touch or behind the times.

Ewan McGregor stars as a hack (with no name) hired to rewrite the memoirs of ex British premier Alan Lang (Pierce Brosnan), a figure obviously modeled on Tony Blair. The scribe’s predecessor was found floating in the waters off Cape Cod and the new book doctor is under the gun in more ways than one to produce a best-selling tome in four weeks. Soon after he arrives at the seaside home where Lang and his entourage are sequestered, news breaks that Lang will be investigated for war crimes in connection with the handing over of terror suspects to the U.S. As he orients himself with help from the politician’s wife (Olivia Williams) and close aid (Kim Cattrall, attempting a British accent), our boozy hero begins his own investigation. The burning question being whether Lang was a puppet of the CIA.

It’s a dangerous game but, alas, he’s never in all that much peril. The stabs at skullduggery are more mood-related than substantive, with tense passages alternating with languorous stretches. The acting is crisp across the board. The ever-reliable Tom Wilkinson adds to the fine work of the principals and Eli Wallach, finally looking his age, has one rich scene. Polanski shows his mischievous side in casting the supporting roles. Along with Cattrall, Jim Belushi makes an appearance as a publishing exec. There’s no shortage of wit and intelligence in the dialogue, adapted from Harris’ book; the yarn is just too elementary and conventional. Despite a couple of twists, the solution to the puzzle borders on the simplistic. Much hinges on the navigation system in a BMW and, per usual, Google is a primary investigative tool.

Story aside, Polanski doesn’t try to do anything original with the political conspiracy genre. For every riveting sequence, he throws in something painfully obvious, such as when MacGregor’s character and Lang’s wife hold hands in the back of a chauffeured car and we know the obligatory shot of the security officer glancing back in the rearview mirror will follow. Again, such easily-anticipated and obligatory choices would frustrate less if the movie had more to say. Polanski and company leave conspiracy theorists (on the left and right) without much read meat to savor -- without any insights into geo-politics, Anglo-American relations, or the writing and re-writing process. The rejoinder that the film is being proffered as entertainment seems  undermined by the fact it’s ultimately quite dull. After a nicely paced opening quarter-hour, it drags, feeling much longer than its two-hour-and-eight minute runtime.

For all of The Ghost Writer’s intended topicality, the most interesting subtext has to do with Polanski himself. It’s hard not to picture the director stewing while under house arrest in his Swiss chalet, anxiously awaiting reports of opening weekend grosses, a lawsuit by Tony & Cheri Blair, and possible extradition to the United States. 

(Released by Summit Entertainment and rated “PG-13” for language, brief nudity/sexuality, some violence and a drug reference.)