In Elmer Rice’s thickly populated “Counsellor-at-Law,” following the rules hardly seems like an option. In fact, if you stick to the letter of the law, you will wind up tightly wound, alone, and possibly wavering on a window ledge. No, far better to embrace the roiling atmosphere of the 1930’s: Don your fedora, snap its brim, and light out for what you can get.

In this case, if you hie to St. Clement’s, you can get a jam-packed evening of buzz-saw accents, pistol-packing dames, and a barrage of every caliber of betrayal. Before the night is over, class, fidelity, community, ethnicity, idealism – even the occasional law – will lie crumpled on the floor. And you will have had an exhaustingly good time.

Delineating each little tragedy played out by this cast of 21 would take more words than my editors allot. Suffice it to say, the stage is awash in turmoil, from unrequited love to communist persecution. At the vibrant center of it all stands, or rather fidgets, George Simon (John Rubinstein), a high-priced, high-profile lawyer.

After dragging himself by his bootstraps all the way from Second Avenue, Simon still seems like a scrapper, though his office gleams with mahogany and his wife reeks of class. His monstrous step-children decry his Jewishness, but in an office full of Italians, Irish politicos, and Russian supplicants, he’ s actually right at home.

Simon’s success, though, has bred him a host of enemies. When an upstanding member of the community (“the right hand man of the Lord God Jehovah!” George sneers) unearths some dirt on him, George is threatened with exposure and disbarment. His wife (Beth Glover), whose silk suit cloaks a treacherous heart, can’t take the heat. While somewhere in the city she loads her trunks onto the steamer for Paris, George and his loving assistant Miss Gordon (Lanie MacEwan) call in favors, dole them out, and try desperately to clear his name.

The Peccadillo Theater Company delivers Rice’s dense, delicious slice of the American legal industry with brio. Director Dan Wackerman claims to be a custodian of “lost classics” and here he shows the necessity of that service. Rice’s office epic deserves a higher rung on the theatrical ladder: It’s got twice the relevance of “Street Scene” and 10 times the fun.

Mr. Wackerman makes the most of the rat-a-tat style, packing Chris Jones’s massive, nimble set with a startling cast. Special mention has to go to Nell Gwynn’s Mrs. Chapman, a bass voiced man-eater who steals her few scenes, and the delicate Mary Carver as George’s suffering mother. The lynchpin of the entire endeavor, though, is George himself.

John Rubinstein’s incredible performance is both big enough for the style and minutely detailed enough for long examination. He revs like an engine, barely able to sit down, kicking his buddies in the pants and roaring at his secretary. For a man in existential crisis, he sure has a lot of energy. Lucky, since the demand of the role is absurdly large.

Not only does George deliver reams of words, but he must somehow shoulder the burden of standing in for the American dream. This means remaining lovable while buying politicians and indulging in a bit of insider trading on a vulnerable stock exchange. Even while up to his eyes in graft, he remains a staunch friend, a hero to his neighborhood, and the apotheosis of his mother’s hopes and dreams.

Capitalism, especially as reveled in by George Simon, barely pauses for ideals – that itself is taken as an ideal seems hilarious. Simon does take stock – a young communist firebrand makes him reflect at one point, and his emotions take a beating from his slithering wife. But defeat just isn’t in this guy’s vocabulary.

Not really by hook, but mostly by crook, George prevails. If your own heart quivers at the idea of a three-hour play about lawyers, take a page from his book. Roll up your sleeves, and dig in.

Until March 6 (423 W. 46th Street, between Eighth and Ninth Avenues, 212-868-4444).