Open Monday through Friday, 11:30 a.m. to 2:30 p.m. and 6 to 11 p.m.; Saturday, 6 to 11 p.m.; Sunday, 4 to 10 p.m. BA, MC. Reservations.

Food: Great beginnings and happy endings

Style: Eighteenth-century splendor

Price: Main dishes about $4 at lunch, double at dinner

EVEN IN A neighborhood so beautifully restored as Alexandria, Cafe Lafayette stands out as an eighteenth-century showcase, probably now more grand than its tinsmith-shop origins. Beyond restoring the classic plasterwork and furnishing with darkly gleaming tables, silk-upholstered chairs, antique sideboards and enormous portraits of greater size than artistry, the Cafe Lafayette has paid attention to the kinds of details that represent the gracious life. Wines are served on silver salvers. A guitarist plays softly in the evening. The china is handsome, the carpets lavish. And those two symbols of festivity - candles and flowers - are employed with abandon. Tall white tapers in hurricane lamps, on tables and sideboards, illuminate the dining rooms and throw their glow the street in front of the restaurant. Silk flowers decorate the hostess desk, fresh carnations the ladies' room. On the tables there might be a single carnation or a tiny bouquet.

The groundwork was laid for memorable evenings. The menu was designed to entice - with caviar and cream cheese turnovers to start, key lime or chocolate mousse pie to end, twenty inventive main dishes in between.

It is the in-between that is the problem. The dinner is bound to start out favorably disposed to the Cafe Lafayette. The waiters behave with practiced correctness. The appetizers please - the airiest of fried turnovers, plump with caviar and cream cheese, or mushrooms stuffed with chopped chicken livers, drenched with cheddar cheese. The soups are richly flavored, the spinach and mushroom salad piquant with sour cream and dill. The wine list is small, select, and reasonably priced - averaging $8 to $11 - with two wines labeled especially for the restaurant.

But later in the evening the flaws begin to show. The waiters grow lazy and let you pour your own wine. The chicken enchemise turns out to be orangy-sweet overcooked breast meat in an undercooked pastry. The lamb chops are burned, drizzled with a sauce acrid and starchy, bearnaise being its pseudonym. The seafare's catch of the day tasates like yesterday. The veal scallops have been mercilessly pounded in hopes of disguishing their mediocrity. It was hard to reconcile the parade of disappointments with a lunch of quiche whose flaky crust surrounded an exquisitely delicate seafood custard, and chicken salad of such moistness and freshness that it seemed a different species from that dinner chicken en chemise. At lunch and dinner the vegetables were well executed and fresh, the herbed cheese bread feathery and zesty, nearly the texture of cake. But at lunch, the fine main dishes cost $3 to $4.At dinner, the kitchen's dismal overextentions cost $7 to $8. In both cases, appetizers averaged $2.50 to $3, desserts $1.25 to $1.75.

And in both cases the desserts defused amy possible previous disappointments. The chocolate mousse pie, creamy and bittersweet, was bettered only by the tart ley lime pie, pale yellow, well laced with shredded peel and topped with meringue. Then there are bananas sauteed with rum sauce, or dense bittersweet chocolate sauce over ice cream. And superior coffee to top to off.

Lunch is crowded, and justifiably so. If the crepes reuben, chicken Lafayette and cottage pie are as well prepared as the dishes I tried, one could lunch often and well, and the cost - $5 to $10, depending on your appetitite - would be well repaid by the graceful setting. But dinner falls short, for then the price is steeper, the leisure allows one to note the edge of indifference in the service, and the dishes, being prepared to order, are more subject to slip-ups. Yet, with such success in the beginnings and endings, one has hopes that the Cafe Lafayette will get around to straightening up its middle.