Nothing has prepared us for the astonishing exhibit that goes on view tomorrow at the Corcoran Gallery of Art. "Northern Light: Realism and Symbolism in Scandinavian Painting, 1880-1910," is so good it is scary. It will leave the viewer shaken. It will shake his insular, comfortable assumptions about early modern painting. It will expand his list of masters. It will also show him ghosts.

A sense of unreality, of spirits conjured from the dark, haunts this exhibition.

Why have Americans never before been shown the paintings of Prince Eugen, a brother of a Swedish king, whose landscapes predict Mondrian's? Why have we not been shown the art of Norway's Christian Krogh, who helped teach great Edvard Munch of Norway how to portray death? How have our museums, dealers and historians so long overlooked Denmark's Vilhelm Hammershoi, an extraordinary artist whose enigmatic paintings are as intimate as Vuillard's and as strange as those of Balthus?

Of the 36 painters represented, there is only one, Munch, whom Americans, so far, acknowledge as a master. But there are other masters in this show.

Their painting was advanced, their art was deeply serious. And the best of them were more than daring, skillful painters. They were seers, too.

Perhaps it was the heavy darkness of their Nordic winters that taught them to see everywhere the opposite of life. It may have been the glow of their endless summer nights, whose silver light kills shadows and brings spirits into sight. All have glimpsed the face of death. His darkness, or his chill, is seen in almost every picture in this show.

We sometimes see him fully, with his wings of leather, his skeleton, his scythe. In Christian Krogh's "The Sick Girl" (1880-81), he hovers in her eyes. He haunts the flowered graves of Harald Sohlberg's moonlit landscapes, and the sooty chimneys painted by Bjo rn Ahlgrensson of Sweden and Halfdan Egedius of Norway. The predatory crow that pecks an abstract ground in Akseli Gallen-Kallela's Finnish painting of 1884 seems to be his messenger. Vilhelm Hammershoi's Danish rooms would seem wholly empty if he were not there. He is most fully seen in that black figure on black that gestures from the doorway in Harald Slott-Moller's 1888 "The Poor: The Waiting Room of Death."

His presence is felt, too, in trees that seem to moan, in rocks that seem to crawl, and in the wild brushwork of Euge ne Jansson's nearly abstract wild nights. Often he is glimpsed -- in Munch's art and in Niels Bjerre's, in Prince Eugen's and in Ludvig Find's -- in shadows that appear to be alive.

This somberness has touched the prayers of Soren Kierkegaard, Ibsen's plays, and Strindberg's, and the films of Ingmar Bergman. What makes this art astounding is not the darkness in it, but the way it seems to trace a previously unimagined path from perfumed, Francophilic 19th-century painting into modern art.

Like so many 19th-century Americans, these early Nordic modernists, Krogh and Munch and many more, were seduced for a while by the advanced art they found in Germany and France. With threads picked up abroad--the high finish of German academic painting, the revolutionary realism of Zola and Courbet, the colors of Impressionism, and its broken brushwork--these artists, once at home again, wove something wholly new.

It is an art that seems to give an eerie, equal stress to the ghostly and the real. Its sense of innerness, of distance, of the spiritual acknowledged, makes it seem so modern. This art avoids the easy. In it we can feel a revolutionary sense of the past rejected. Its naturalism is a kind of newly discovered nationalism. Like those American painters who, returning from Munich, Dusseldorf or Paris, set out for the seacoast or the Rockies, these artists turned to Nordic nature, to her birch woods and her lakes, her darks and her midsummer nights, to regain their own land.

This show is so surprising in part because we have been blinded for too long by our loyalty to the art of our own land, and to that of France. There is another reason. The masters represented were recognized early at home. They have not appeared often on the market, or in our museums, because their pictures were bought where they were painted when they were still new. "The great masterpieces of turn-of-the-century Scandinavian art -- even those of artists like Edvard Munch who were internationally admired in their own day -- " writes Tone Skedsmo, in the exhibition's exemplary catalogue, "are to be found without exception in Scandinavia itself, and primarily in public collections there."

Half this show could go tomorrow into the permanent collection of the National Gallery, the Metropolitan or any other great American museum. It is as fine as that. And yet such institutions hardly seem to know that these works of art exist. That is sure to change. This show will make a difference. It will readjust our reading not just of Scandinavia, but of the rise of modern art.

Kirk T. Varnedoe, a Manhattan scholar, chose the pictures and, with his students, organized the catalogue. Although it opens here, "Northern Light" was organized by the Brooklyn Museum. Its stay in Washington is brief, five weeks. It will go to Brooklyn and then to Minnesota after closing at the Corcoran on Oct. 17.