This place is so busy that they answer the phone with a taped message (in a French accent, of course), and it's so far out of town you may need Dramamine to cope with the narrow, roller-coaster roads. So why bother? Because the country setting is terrific, the French cooking mainly good, the wine list extensive and fairly priced, the service warm and attentive. And the cost of the whole thing can be moderate if you order carefully -- beware, for example, that certain appetizers, desserts and beverages are included in the price of the entrees while others aren't, and, for maximum economy, note the special $14.95 dinners. Although the menu changes daily, there are high points: meats in puff pastries, for example, including a delightful garlic sausage appetizer and delicate shellfish-in-pastry entrees. A fine old favorite is salmon topped with a cloudlike seafood mousse, and the applewood-smoked salmon appetizer is exquisite. Less exceptional lately have been duck in a sweet fruit sauce, run-of-the-mill veal medallions in an unremarkable cream-sherry sauce and peppercorn steak with a roquefort butter that obliterated the taste of the meat. There are a few quality-control minuses here, too: the bread has been soft-crusted and the dressing on the house salads overdosed with vinegar and apparently poured on rather than tossed. No problems with desserts, though -- look for the dynamite chocolate terrine, the homemade ice cream and the feathery kugel 332 Springvale Rd., Great Falls, Va. 759-3800. D $19.95-$22.95. D daily. Closed Mon. AE, C, MC, V. Res req. Full bar.