Donnie Brasco covers different territory from Martin Scorsese's Goodfellas, but it has the same kind of appeal. As in that film, we get a frank look at the Mafia and how it works. It doesn't paint as broad a picture as Goodfellas, but it does an arguably better job at laying out the rules of the game.

The story centers on two men, a mob guy (Al Pacino) and a fellow (Johnny Depp) he makes "a friend of his," a phrase that implies more than it seems to. The catch is that Depp's character is an undercover FBI agent.

Early on, Pacino fears he is being called out to get whacked. It's always your best friend that does it, Pacino explains. Gradually, Pacino and Depp become best friends, and we think we know how the third act is going to pan out. But the movie is too intelligent to let itself fall unthinkingly into the predictable.

Al Pacino's performance is brilliant. Pacino is at home in these kinds of roles, but he never lets himself go on autopilot. For all the mobsters he's played, his work in Donnie Brasco is still something new. This is probably the most sympathetic mobster role he's had, and the last scene with him could scarcely be more poignant.

It's surprising, though, that a movie that gets the mob scenes so right manages to get a subplot involving Depp's family so wrong. His wife (Anne Heche) is gradually worn down by the strain of her husband being away for days, even weeks at a time doing work he can't tell her about. It becomes too much and threatens their marriage. Understandable, but none of these "home" scenes work. For a relationship to deteriorate, it cannot already be broken, yet it certainly appears to be. Why does Heche's character stick around? Her pain and resentment is not only understandable but seemingly justified, and her simultaneous love for her husband is unconvincing. Likewise, his treatment of her suggests that the important parts of their story happened before the movie started and resumed after it ended. Depp's performance is serviceable enough in the mob scenes, but the character is too inscrutable when he gets back home. What's going on in that head of his?

This is the only area where the film falters. The rest of it is inspired, with occasional forays into greatness. The movie has a thorough understanding of complex relationships and uses them to explore some complicated moral quandaries. It's easy for us to sit back in our couches and discern right from wrong, but if there is one thing this movie shows us, heavy emotional ties can make this decision -- and following through on it -- more than a little difficult.