"Night Prints" is a dreamy show. It is sexier and scarier--and more amusing, too--than most survey exhibitions at the National Gallery of Art. Bats fly, as do snowballs, through its shadowed pictures. Unbuttoned bimbos misbehave and fireworks explode in its master prints.

Its source, too, is unusual. No academic art historian picked its hundred images, its Rembrandts, Redons, Daumiers, Goyas and van Goghs. They were chosen by a doctor, an internist now retired. "Night Prints" is the product of a local amateur.

Her name is Ruth B. Benedict. She is 69 years old. Her hair is gray, her words are curt, the shoes she wears are sensible. She has never been employed in the print rooms of the Gallery. But she's hung out there for years.

"I drifted in," says Benedict. At first she came to study, to compare impressions, to leaf through heavy catalogues, to consult with the staff. "I got friendly with Andrew Robison the curator in charge ." She started showing up every Wednesday afternoon.

"And then one day," says Robison, "she suddenly came out with a marvellous idea."

Making etchings and engravings and lithographs as well ususally involves putting dark forms to white paper. Most Old Master prints (and almost all produced before the days of Caravaggio) show figures bathed in brightness that is the light of God.

But prints that show the life of night--its coziness, its lovemakings, its deaths and nameless horrors--turn all that around. Such prints are on view. Together they remind us that the night belongs to flickerings, to mystery not clarity, to moonglow not sunshine. The night does not exclude the saints, but it welcomes devils. And night prints, unlike others, show light forms against dark.

Robison describes Benedict's suggestion as "one of those ideas that--as soon as it's enunciated--provokes the same response: 'Why didn't I think of that?' "

"Night Prints" is the first museum exhibition to explore its theme. "It stands as an example of the best traditions of the English amateur," says Robison, "in a place as fuddy-duddy as the National Gallery of Art."

"He was very brave," says Benedict. But then Robison--who asked Benedict to search through private Washington collections, and through the 55,000 prints the Gallery now owns--is himself an amateur. He was a professor of philosophy at the University of Illinois before he joined the Gallery in 1974.

The prints--on display in the Gallery's West Building--all have been installed in frames of silver gilt. Their mats aren't white, but dark. The exhibition opens with a chiaroscuro woodcut cut by Hendrick Goltzius, circa 1594, which shows the goddess of the night, an owl at her left hand, being pulled through clouds by a team of large-eared bats. It closes with a Vera Castro etching of skeletons at play from 1962. These prints might have been arranged in accordance with chronology. But Benedict, instead, picked another path.

She decided to display them in nine groupings, which are:

Home, family and friends; Dalliance, love and lust; Supernatural and unnatural happenings; Celebrations, spectacles and entertainments; Readers, brooders and other single figures; Execution, murder and death; Conspiracy, search, flight and capture; Life in city, town and country; and Lyrical and pastoral landscapes.

She calls her groupings "loose ones." They bleed into each other, as things do in dreams.

Edvard Munch's "Moonlight" (1895) is shown here with the "Brooders," though its solitary figure, dissolving in gray light, might well be a ghost. Picasso's "Blind Minotaur Led by a Girl through the Night" (1936) is shown here as a scene of "Search," though it would not seem out of place among "Unnatural Happenings." Nor would Pierre Prud'hon's memorable image of a wading monk embracing a luscious, just-drowned nude, but Benedict has placed that pair among other scenes of love.

Rembrandt rules the show--"as he damn well should," says Benedict. There are eight Rembrandts on view. Darkness moves on darkness in almost every one. Before Rembrandt's "Adoration of the Shepherds: A Night Piece," the viewer has to look, and pause, and look again before he can discern Joseph, dimly lit, nodding off to sleep.

Rembrandt offers miracles. Goya portrays horrors. In his "Hunting for Teeth" (1799), a woman climbs a scaffold and reaches for the gaping mouth of a man just hanged. "Some superstitious people still believe that a corpse's teeth bring luck," says Benedict. "Once, while I was working in a New York hospital, a woman asked for some. Of course, I turned her down."

There are nocturnes in this show, and miracles aplenty, and many wild parties. The wildest may well be a 1735 tavern scene by William Hogarth in which an English wench prepares, by taking off her underclothes, to dance upon a mirror. The show is haunted, too, by ghosts. An 1896 lithograph by Odilon Redon called "And We Each Saw a Pale Light" is perhaps the scariest. Other prints on view will make one laugh aloud. The funniest are Daumiers, and the funniest of all is a lithograph of peeping toms called "Oh Absolutely! The Big One Is Taking Off Her Corset and the Little One Is Looking for a Flea."

Benedict's eye is quirky. Her scholarship is strong. "She is a highly intelligent woman," says Robison. "She thinks carefully and deeply." The prints she has selected, whether old or new, whether raucous or exalting, all are rich and fine.

Benedict, born in Germany, was 7 when her family brought her to New York. She was still a little girl when her mother started dragging her to see print shows at the Met. With her late husband, William (a spectroscopist who discovered hydrogen chloride on the planet Venus), she moved to this city in 1942. She says that she began "bothering the curators" by seeking information from painter Jacob Kainen while he was in charge of the Smithsonian Institution's division of graphic arts. Then, for a decade, she edited the Washington Print Club's witty and iconoclastic newsletter, most of which she wrote. She is now the Print Club's president.

Her exhibition titillates. It terrifies as well. Its images are dark, but together they enlighten. Benedict's exhibit beautifully surveys the remarkable print collections now housed at the Gallery and elsewhere in this city. It closes Sept. 15.