In her 14 years, Leslie Ruley has seen enough horror shows to know that Saturday night can be cruel to baby sitters.

As she climbs the darkened stairs of a house in Bethesda, she listens for thumps and creaks, and remembers movies where "the baby sitter walked upstairs to find the kids were gone or had been eaten by ants or something."

When she finds that 4-year-old Jonathan is missing from his bed, she sucks in her breath. Barely 5 feet tall, her shining, fawn-colored hair swept to one side in ballerina style, she scampers though the other bedrooms, and stops only when she finds the boy asleep in his mother's bed.

The shepherdess of the suburban night is relieved. Like countless teen-age girls who guard the scions of countless subdivisions each Saturday night, hers is a reign of rules and responsibilitiy. It is a young girl's domain, a rite of passage that falls midway between the first pair of nylon stockings and the solo cruise in the family car. The destinations she scribbles on pads by the phone are all she knows of the night life that glitters beyond her quiet streets.

"They've gone to Chadwick's," she says. She isn't sure where this is, but it has a nice sound.

For $1.50 an hour, "or less if they don't think I'm worth it--I always tell people that"-- Leslie Ruley reads two stories, tucks Jonathan and Matthew into their beds, vacuums and shelves the scattered remains of a night of boyhood revelry.

At midnight, she settles into a large, comfortable chair near the television to watch "Saturday Night Live." She scrutinizes the costume of a singer in a band called Men at Work and decides that if she were on television she would try to wear nicer clothes.

The kitchen at midnight holds no rewards. There are no Doritos. 'I can't believe it. They always have Doritos." The granola bar box is empty, too. She is too tired to open her school books, so she watches the flickering screen. She listens for the children and the sound of the latchkey at the door.