Lucky Number Slevin is the kind of disappointment that, maddeningly, hypes up your expectations before crashing and burning. Maybe my language is too strong -- it's not a bad movie -- but mediocre movies should at least have the decency to announce their intentions up front.

The movie starts wonderfully. The first 30 or 40 minutes are electric, absolutely sizzling with great, funny, rapid-fire dialogue. A case of mistaken identity unfolds, and a young man finds himself caught between two warring gangsters who think he owes them money. One offers to forgive the debt in exchange for a small favor, the kind he can't refuse. It's fun, energetic, and establishes a frothy comic tone that carries us through moments of sudden violence. And then, in the second act and more so in the third, the movie loses its way. The nimble dialogue sputters and dies, and in its place comes an unsavory meanspiritedness. It's like a good diet drink: you're pleasantly surprised at how it tastes, but the nasty aftertaste inevitably kicks in and lingers. I can't say much more without revealing the movie's many twists and turns, but suffice it to say that the movie thinks we should be rooting for individuals every bit as ugly and unconscionable as the acknowledged badguys. I can't do that, and the movie left me with no alternatives to root for. When the plot finishes unfolding, all that's left is an ugly mess, and I felt enervated and morose.