There's something about a Robert Ludlum story that's simply irresistible, like a Snickers bar or Rocky Road ice cream. They're not good for you, there's no nourishment in them, you won't find any of the proper food groups, there's no challenge to mind or body; only a pure sugar rush that evaporates a couple of hours later. You can't say one good thing about any of them except that the adolescent in you has to have a fix every once in a while.

That's "The Bourne Identity," and like every snuck bite of a Snicker it was a delicious treat. Matt Damon is Jason Bourne, and when we meet him he's a body in a wet suit floating on a storm-tossed sea. Picked up by an Italian fishing boat off the coast of Marseille he has what appears to be the ship's cook remove two bullets from his back along with an implanted packet of information from his hip. When he wakes he has, yes, no memory. He doesn't remember his name, he doesn't remember anything before two weeks ago (though since he obviously wasn't floating in the Mediterranean that long he should have remembered how he got there, but let's not be picky).

The little packet has the number of a bank account in Zurich, and from that account he takes a huge amount of U.S. dollars and puts them into his little red backpack. But even as he does it he is being watched by - I'm not giving anything away here - the C.I.A., which wants him dead; and in about five minutes, directing things from Langley, Va., assembles a small army of shooters to do it. But Jason is not without resources of his own. He can scale walls, kill with many karate-like chops, and so forth. He knows his way around, even if he doesn't know much else. He meets Franka Potente, which is the first good thing that happens to him, and escapes with her to Paris, where he hopes to find out who he is. The rest of the film is, we have to say, more of the same, and I enjoyed every minute of it.

Those who are out to get him are Ted Conklin (Chris Cooper) and Ward Abbott (Brian Cox) of the C.I.A., who exist in this film only to provoke Jason's next hairbreadth escape from them and their minions, including one who, when he realizes he has failed, does a deliberate backflip out the window to his death. Oh, that C.I.A. It seems that Jason was an operative whose mission was to kill a - oh, never mind. It's just a MacGuffin anyway, which is a term invented by Alfred Hitchcock to describe something - an object, a quest, a mystery - that drives the plot but is ultimately shown to be irrelevant. Think of the briefcase in "Pulp Fiction."