Never date a spy, much less marry one. That's one of the important lessons (maybe the foremost) to be reaped from "The Good Shepherd," Robert De Niro's second film in the director's chair after his debut "A Bronx Tale" in 1993.

Whereas his first was a compact, manageable story about boyhood in the Bronx, "Shepherd" is surprising for the grandiosity of its theme (the birth of the CIA seen through the eyes of one agent), scale (spanning three decades from the 1930s to the end of the 60s — World War II. the Cold War, and the Cuban Missile Crisis) and length (close to a whopping three hours).

It's weighty, ponderous and self-important which can almost be a description of De Niro himself at times, but in this case, the adjectives have only positive connotations and are well-deserved (Who has a right to be self-important if not De Niro?) The film, on the other hand, flounders in its own sea of seriousness at times, and even the director's excellent cameo performances of a conspiracy-mongering general (you know, the kind with a bad foot and a glass of whiskey permanently clutched in one hand) can't quite rescue it from being swallowed up in the waves. But De Niro gets his point home, through his acting and directing: that spy-life is often utterly banal and aggressively ordinary. Typically, it's years of drudgery punctuated by the exchange of manila folders that may or may not contain top-secret information. The general, for all his power, seems to hit the high point of excitement at Christmas, when he's wheel-chaired over the eggnog and given a big cup. It's said that Hitler's regime succeeded so well because it was run by inconspicuous clerks, not hot-blooded military heroes — after "The Good Shepherd" you'll believe it too. Wars and espionage are engineered by men who quietly, unobtrusively, relentlessly, tend to their flocks. Day after day after day.