FREDERICK FORSYTHE has adapted his own book into an absorbing, intelligent and suspense-filled film. Directed by John Mackenzie ("The Long Good Friday"), it's streamlined and rich at the same time -- like the best of the James Bond films, but serious.

You'll need all your mental motors running to follow the story but basically it's about how easy it is to assemble an atomic bomb and detonate it in an enemy country. And the ubiquitous Michael Caine, as British super-agent John Preston, is on the trail of a Soviet plot to do that very deed. His target is the murderous Maj. Valeri Petrofsky (a surprisingly deft Pierce Brosnan), who has set up housekeeping near an American airbase in England and has all the bomb parts.

Forsythe and Mackenzie give us something better than run-of-the-mill spyflickia. Instead of stunt-car chases, hyperbolic gunfire and larger-than-life villainy, this is a slow dance on the chilling ground. Preston must track Petrofsky with meticulous detective work, as well as play bureaucratic games to satisfy his jealous department head (Julian Glover). And Preston is always -- maddeningly -- one step behind Petrofsky.

Besides the smart exposition, Forsythe injects memorable dialogue: "I hope they didn't pay you in cash," British agency head Nigel Irvine (Ian Richardson) icily tells an agent caught giving secrets to the South Africans. "The rand's taken a bit of a dive lately." Soviet Gen. Karpov (Ray McAnally) threatens someone with being placed "in an open jeep in Afghanistan." Petrofsky declines a drink from an American airman with: "I usually try to stop after a gallon or two."

"Protocol" is espionage as exhilarating as the better Bond but with less of the winky camp. This is deadly stuff: We see just how easy atomic terrorism would be.

One sequence particularly stands out -- when Petrofsky and an attractive KGB nuclear technical officer (Joanna Cassidy) assemble the weapon in a safe house. In Mackenzie's hands, the scene becomes a combination of fearful tension and edgy eroticism, as the two agents manipulate each other as well as the bomb.

"Protocol" has some potentially confusing double-agent pirouettes and last-minute treachery, and the ending seems rather abrupt. But "Protocol," with its abundance of strong performers (including Caine, Brosnan, Richardson, Cassidy and Ned Beatty as doubler Gen. Borisov), is not so easily dismissed.

THE FOURTH PROTOCOL (R) --

At area theaters.