It's like this. Having graciously paid tribute to Scorsese's Mean Streets, Bad Lieutenant throbs its way through opening scenes detailing a descent into depravity - Harvey Keitel on a terminal nosedive into corruption, drug addiction, gambling. Stylistically extraordinary, the film frees itself from dialogue to observe in shuddering, mutant close-up.

So far, so ugly. But harsh and potent though it is, masterpieces are made of much more. Halfway through, Ferrara takes on new agendas. He stops making an excellent Scorsese clone, he starts making King Lear for the nineties.

Like Lear on the heath, Keitel is left to wrestle with his conscience. He gives the performance of his life, dredging up dreadful shrieks and howls from the bottom of his soul. No longer hedging his bets or pleasing his sponsors, Ferrara goes with it. The themes get no bigger - sin, guilt, forgiveness, redemption, all tackled with a monstrous force that slams into you and leaves you almost physically winded. For all this, it is a film of hope - indeed, that's why it's so difficult to take.

The first time I saw it, it took everything I believed in and scattered it in the wind. Brighton Marina is a desolate place at the best of times - Charter Place by sea, if you like - but it was bleak beyond comprehension on that afternoon. It crushed me, it left me unable to focus on anything, staring out to sea and stumbling home.

Like I say, watch it if you want.