Open for lunch Monday through Saturday 11 a.m. to 5 p.m., for dinner Monday through Thursday 5 p.m. to 10 p.m., Firday and Saturday 5 p.m. to 11 p.m., and Sunday noon to 10 p.m. MC, V. Reservations suggested on weekends.

Prices: Dinner appetizers $2.75 to $5.25, main dishes $7.25 to $13.95.Full dinner with modest wine, tax and tip about $18 to $26 per person.

How much can you learn about a restaurant just by casually walking in and looking around? Try it with the Calvert House Inn. Your first step once inside the door is to take in the room. Notice the dark paneling, rubbed to a high polish; the snowy linens, with the napkins painstakingly folded into fan shapes; the fresh flower on each table; the warm glow of the lighting. Put those visual clues together and they spell "trying hard."

Now ask to see a menu.(Don't be shy. Being a careful consumer applies to restaurants, too.) Read the Calvert's menu carefully, because the message isn't obvious. At first glance, it seems to say "same old stuff" -- crab cakes, crab imperial, a couple of skewered things, even (dare we say it?) surf 'n' turf. But look again: of the 12 seafood items, only one is fried. And what's that among the appetizers? Spinach pie? Stuffed grape leaves? Things are looking up. Time for you to toss off a casual question or two. "Is the fish fresh?" you ask. The young waiter doesn't hesitate. "Sure is. They go up to Baltimore to buy it." Now shift your eye to the dessert page and ask if they make their own pastries. "All of them, except the cheesecake." Add a few more mental points for that, notice the reasonable prices and by this time your pulse should be quickening: this place could be a find.

It is. The Calvert House has been around for a long time, but for the past year it has been owned in part by the Salimi brothers from Iran, who do all the cooking. They're turned it into a rare oasis along the highway wasteland.

If you've eaten spinach pie in enough restaurants, you can gauge it pretty well before you've tasted the first bite. Does it stand up puffy on the serving plate? Is the surface dry and silky, free of oily film? When you press a fork to it, can you hear the phyllo layers crackle smartly? For the Calvert's rendition, yes, yes and yes. And the spinach inside is bright and lively, with just the right proportion of feta cheese. High marks, too, for the excellent stuffed mushroom appetizer, but the limp, wet grape leaves fall flat, the steamed shrimp are a bit tired, and the otherwise flawless claims casino have an oversalted sauce.

The soup of the day is homemade and generally first class. But the crab soup, always available, is truly formidable. It's nearly solid with crab and vegetables, and practically free of shell and cartilage, a minor miracle in itself. With its chunky tomato and cabbage, it has the flavor of a borscht that's been to sea. Don't pass it by.

The waiter wasn't fibbing about the fish. The catch of the day is absolutely fresh and broiled beautifully. All it gets, and all it needs, is a little butter, lemon and wine. (Ignore the occasionally available pan-fried fish and the fried shrimp, both ordinary.)

The Calvert's carb imperial turns out to be a lesson in what this dish ought to be: solid, not runny; chunky, not Pablumsmooth; a bit sharp with mustard, not bland; and, above all, free from the cloying domination of mayonnaise. Exemplary as the crab imperial is, you may not want to commit yourself to a full order. Instead you can sample it in the excellent stuffed mushroom appetizer; among the entrees, try it in the equally good stuffed shrimp or in the rather more unusual stuffed oysters, in which the imperial plays a neat counterpoint to the briny oyster flavor.

There's also a how-to-do-it lesson in the impressive crab cakes: broiled, mercifully batterless, slightly peppery and consisting mainly of crab, not bread crumbs. (We have a fantasy about sending bad seafood cooks to a place like this for rehabilitation.) Notice, by the way, that there's a combination platter with a sampling of the crab cake and stuffed oysters (and thus the crab imperial), along with an acceptably good flounder filet and excellent broiled shrimp and scallops. (The broiled scallop entree is probably a very good choice, too.)

Shrimp scampi (jumbo shrimp in butter, lemon, wine and lots of fresh garlic) is excellent, with what tastes like just a hint of nutmeg. Shrimp Calvert, in an herbed, tomato-based sauce with wine and grated cheese, is a livelier, more ingratiating dish. It could be a winner if it weren't for excess saltiness in the sauce -- the same problem that afflicts the clams casino.

For nonseafood types, the chicken kebabs are acceptable, if a bit dry. But the chicken and broccoli (or the sometimes available version with sweet green and red peppers) is marvelous: moist, beautifully trimmed cubes of stir-fried chicken breast with plenty of fresh mushrooms, in a light sauce finished with a touch of white wine and cream.

Among the dinner vegetables, the best choice by far is the impressive fresh mixture, usually with broccoli, carrots and cauliflower. Salads are nothing much, but you shouldn't need one; entrees come with a delightful blend of diced cucumber and tomato in a good vinaigrette dressing enlivened with a bit of mint.

We wish more restaurants had the good sense to do just a few desserts and to them very well. The waiter was right about this one, too -- the cakes and pastries are made in house, and impressively so. Carrot cake, when they have it, is a master work, nearly as moist and solid as fruit cake, with nuts, raisins and what tastes like cinnamon and ginger. Almond cake has almost an angel-food featheriness. There's Haagen-Dazs ice cream, and for an additional 75 cents you can add fruit or liqueur to it.

Sound super? You're right. Riverdale never had it so good.