ROBERT DE NIRO'S ambitious and long film The Good Shepherd is essentially a movie with a miniseries trying to burst out of it. De Niro gets tangled up in ways that bear comparison to The Godfather III: he gets stuck in a snarl of subplots. Eric Roth's script mutters about conspiracies like a bag lady, hinting at darker schemes that the film is not at liberty to mention.

The Good Shepherd commences in mid-April 1961 with the bungled invasion of Cuba at the Bay of Pigs. The way the film tells it, someone leaked the secret invasion plans to the Cubans. In a morsel of Mametian euphemism, a spy master explains, "We have a stranger in our house."

After the debacle, the Central Intelligence Agency retrieves a fuzzy clandestine film of the instant of the leaked information. The security breach occurred during pillow talk between an unknown man and his lover. As the lab tries to identify the time, the place and the participants, De Niro flashes back to trace the life and career of CIA officer Edward Wilson.

Matt Damon plays Wilson through more than 20 years of history. Tapped for Skull and Bones at Yale, he is later chosen for the OSS by Gen. "Bill Sullivan" (i.e., Wild Bill Donovan). De Niro plays the officer as a tough, profane patriot, who later prophecies trouble about the danger of establishing a secret service—as well he might have, seeing all the coups and debacles on the CIA's CV.

Wilson spends the next two decades rising in the agency. Acts of betrayal inflame his lack of trust in the outside world. The first treachery comes from a college professor (Michael Gambon). Later, Wilson works with a double agent (Billy Crudup) based on Kim Philby. (You have to know the story of the Philby scandal to understand this part of the movie.)

As the years pass, Damon's pushed-in face hardens from chronic stonewalling. Eventually, he gives a performance that ought to be moved around with a forklift. Wilson has a melting side, though; he is unusually culpable to what espionage lit calls "a honey trap," especially if the lady in question is deaf. (It's not every day that you get to hear about a really new fetish.)

Tammy Blanchard plays Laura, the one figure who represents Wilson's lost possibilities, his chance of escaping his life of secrets. As Stacy Edwards did In the Company of Men, Blanchard makes the accent of a deaf woman seem alluring, softly drawling.

The Good Shepherd suggests that part of Wilson's tragedy results from his hasty marriage to a senator's daughter, nicknamed "Clover" (Angelina Jolie). There is such a thing as a beautiful yet desperately insecure woman. Still, such a woman ought never to be played by Angelina Jolie. Seeing Clover tackle the virginal Edward in the bushes, you figure she needs a patsy more than she needs a husband, but it is meant to be true love. Few actresses can enliven the wife-who-waits role, especially when the wife asks such rhetorical questions as "What are you going to do, Edward, save the world?"

Clover comes from the class of people who own sailboats and tennis courts as consolation for personal disenchantment. So it is strange to see Jolie turning as pale as the last rose of summer while her husband holes up in dark rooms in London and Berlin. Clover's real purpose in the story is to mother the next generation: Edward Wilson Jr., played in adulthood by Eddie Redmayne. Junior is the stereotypical angry, introverted pants-wetter whose father goes away on business too often. Inexplicably, Junior becomes a New Frontiersman who wants to join his father in the CIA.

From the uneasy way he treats this life, we see clearly that De Niro finds the WASP world absolutely foreign and daunting. He reveals its rites without any preparation, in the same way Coppola sprung the Sicilian customs on the audience without warning in The Godfather.

De Niro wants the scenes of the glee clubs and the Hasty Pudding show to chill our spines; at the former, Damon turns up in a dress singing Gilbert and Sullivan's "Poor Little Buttercup." The film treats the CIA as dangerous and soul destroying but offers only sketches of the agency's record of ineptitude and high-handedness. It wasn't just a real-life leak to the Russians that made the Bay of Pigs fail. And better arguments against the CIA exist than just claiming it causes its employees to neglect their families.

Let's be fair, though. It is fun to see Jolie with her hair down, squeezed into Rita Hayworth gowns. The Good Shepherd is the kind of film in which it seems like something is always just about to happen. The film's size, however, does this beast in; it is long, but not long enough to unveil its huge canvas without cutting out characters and motives.

And the canvas has a hole in the center: Damon's Wilson—an anti-Jason Bourne who always does what he's told—doesn't have enough greatness in him to be sacrificed. The Good Shepherd starts like Le Carre and tries to end as Mario Puzo. The final, flamboyant assassination presents a baffling spectacle; it is there only to assure the audience that something really happened in the movie.

The Good Shepherd (R), directed by Robert De Niro, written by Eric Roth, photographed by Robert Richardson and starring Matt Damon, Angelina Jolie and De Niro, opens Dec. 22.

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