FORTY-SIX years ago, a correspondent for The Sun described the end of the Hungarian uprising against Communist rule as if Budapest were Baltimore. Imagine, wrote Edward C. Burks, that Soviet tanks were plowing their way up Charles Street, picking out the main buildings and blasting them to pieces. Imagine that 20 tanks were pumping hundreds of shells into the Post Office, and others were chewing up Mercy Hospital. Imagine your own street, with tanks firing into houses, killing those inside.

It was a graphic and effective way to tell the story of a hard-to-imagine catastrophe.

Now Baltimore is cast as stand-in again, this time as the city that endures a nuclear blast set off by terrorists in the movie The Sum of All Fears. Though the critics hated it, American audiences made it the top film of this past weekend, shelling out $31.2 million for tickets to watch Ben Affleck almost catch up with the plotters before they incinerate most of the real estate between the Inner Harbor and Pigtown.

The explosion is not depicted as a special effects tour de force, thankfully. Accurately portrayed, according to experts, it is instead a sobering and deeply unnerving moment. At one showing, on Sunday, the sense of unease in the audience as the blast became inevitable was palpable.

For years, people have known that a nuclear explosion in an American city was possible. But who could make sense of it? The Sum of All Fears, wheezing plot and all, opens a window. The theoretical becomes powerfully visual, and because it is visual, it is emotional. And now, for any American audience, there is as well the unmistakable shared visual memory of Sept. 11.

It can happen. More than ever, we can imagine it. Because of the film, the U.S. Customs Service felt obliged to reassure the nation yesterday that it could probably stop just about anyone trying to sneak a nuclear bomb into the country. That's more difficult to imagine. About 370,000 containers arrive in the Port of Baltimore alone each year.

A nuclear disaster seems distressingly more likely than at any time for decades. The worry now isn't a massive Russian attack or even so much the potential of Russian "loose nukes" - it turns out that the threat could come from any number of other murky directions. Meanwhile, India and Pakistan are bristling at each other.

The Sum of All Fears needed a setting, and the producers chose Baltimore. It could have been anywhere. ... It might still be.