SETTING IT UP Rooms at the Robert Morris Inn range from about $20 a night to about $60, and the more romantic room is, the more it's likely to cost you. A complete brochure is available; write to the inn (Oxford, Maryland 21654) or phone 301/226-5111. Owners Ken and Wendy Gibson are a friendly young couple who've been at the inn since the days before they could afford to own it. Room arrangements vary with the price. There are those in the original section, double bed with water view and private bath (price for that is as bad as it gets for original section.) Or get one with twin beds and shared bath. Prices at the Lodge vary, too, based on water view and porch. Water view here is the luxury of viewing/reading before the lolling Choptank. From the Chesapeake Bay Bridge take U.S. 503-301 to 50 east to Easton, then Route 333 to Oxford.

There may be those who really believe that "the best surprise is no surprise," with hotel rooms with Old San Juan to the damp innards of Baton Rouge all offering the same comfort-controlled temperature, the same dull art and even the same-gauge metal mattress ticking. All that sameness is supposed to insure a lulling comfort. And, perhaps, the tiniest trace of . . . ennui?

Daily sameness can turn into a real killer of, how shall we say, those delicate, personal relationships between man and woman - which are a little tentative anyway, nature's balance between the sexes being what it is.

To fight the tedium, Marabel Morgan, the grand dragon of total woman, urges black garterbelts and frisky nightwear; the difference between surprise and shock is subtle, though, and for all her good intentions Morgan isn't beyond letting you hang yourself.

But you can preserve the verve, or restore a relationship that's been ground down by the daily grind, without sending your beloved into shock. To put one over on your mate without winding up feeling like a reject from some est camp, abduct your darling. Suddenly.Physically remove yourselves for a jaunt/night/weekend-depending on the time you both have to spare. And the money. The term "kidnap" comes to mind, but ignore it: This is romance.

Your scheme shows how much you really care with a creative, affectionate gift while getting you away from every stupid distraction that's been causing you to bite each other on the back of the neck for weeks. You get off to yourselves and let spontaneity - the best elixir - do its work.

Proceed with meticulous attention to the petty parts and a solid, well-thought-out plan, right down to credit cards, camera - and film - road maps. Clothing. Both of yours. No one is thrilled to arrive in some remote place and learn that there won't be any underclothes for the next three days.

So have both sets of clothes packed and in the trunk of the car, along with the camera and a chilled bottle of wine. And grooming aids for both of you - don't forget the social amenities that attracted both of you in the first place. A razor, for God's sake, and shaving cream. Toothbrush and paste, and floss, if he's big on dental hygiene. His good-smelling cologne, not the stuff your aunt gave him that smells like blackfin crab oil. Any other personal things you've seen stuffed into his bags before.

Pick the place with care. There are many country hotels around, out of the way but within esasy reach. There are old in-town places that make you feel like you're on Baker Street in Holmes' London. Don't schedule yourselves for some fish camp in Chincoteague if you have a hunch that the smell of fish-cleaning makes him gag. If he's always like California for the progressive architecture, spare him an all-nighter in quaint, antique-riddled New Market.

One idea - and an excellant one, from personal "quiet removal" experience - is the salt air and general cheer of the Eastern Shore. Nothing in horse country seems quite an appealing as that salt spary air.

The Robert Morris Inn on the Tred Avon River in Oxford (about ten miles from the mini-burg of Easton) is a perfect choice for a restorative overnighter or weekender. Something in crossing the Bay bridge sets the tone of flight, and of freedom: a definite feeling of separation from care-worn reality that feels like the first day of vacation.

The inn has been standing since 1710, which makes it a pretty interesting place; add its immaculate condition and authentic atmosphere and you have the classic American country inn. And the food is real, with a home-baked flavor. One of its stapbles, in fact, is fresh bread.

Atmosphere, one of the things you'll be counting on, includes you choice (if you call early enough) of rooms with hand-made paneling. The fireplace were built of bricks made in England that came here as ballast in sailing days. Ships carpenters built the house with wooden pegs, ships' nails and hand-hewn beams. In the original section of the main inn (there are several additions and separate cottages), flooring in the upstairs hall is Georgia white pine. And it still shines. And there are no phones in the rooms, no television!

An enclosed Elizabethan staircase leads up to the rooms. Interior decor leans toward expensive-looking reproductions, with Victorian flourishes in the hall and sitting room. The dining room has murals of American scenes, copies of samples used by wallpaper salesmen 135 years ago. Jackie Kennedy found the original paper in an old Maryland house in 1962, legend says, and installed it in the White House.

The inn, a 27-room patch of yellow sunshine, stands three stories high at the foot of Morris Street, dominating the riverfront at the public ferry dock. And because the Morris name figures so prominently in American history, the inn's size and location have made it, literally, the center of Oxford. Down the road, graceful tree-lined lanes and gleaming old houses enhance the view.

Robert Morris Jr., who came to America in 1747, took on the job of financing the Revolution; without his personal aid, it's said, George Washington's army would have scattered early, before the colonies could develop a financial system.

But you can read all about the Morris family and the inn once you get there; let's get back to what else you can do. The tiny town of Oxford, in its last 300 years, has been just about everything bigger cities have been: first one of the busiest ports in the early colony, then asleep for about a hundred years, and now, because the inn is there and the view is beautiful, a pleasure town of little boats, fishing, marinas and not-so-chic little shops that offer shell craft, jewelry and sailing clothes. What it is, also, is secluded. If you want bright lights and nightlife, you may have to drive into Annapolis (about halfway back to the District).

Nothing in the village is out of sight of the Tred Avon River, so if you decide to walk you won't get lost-and you should take a stroll there, especially on The Strand, a sidestreet that takes you to the other Morris place, the Lodge complex, which faces onto the Choptank River. Depending on the season, there will be sailing, fishing, hiking, birding and hunting. Bring your favorite book, and one for your mate.

Plan to spend a lot of time in the dining room, since the style there is leisurely and the food quite good. They have the usual supply of wines, champagne and a specialty drink served in a souvenir glass that will cross your eyeballs if you venture two before dinner. Major specialties are Eastern Shore seafood - mainly oysters and crab dishes. (They serve oysters year-round). If you can walk forward, have a nightcap in the adjoining tavern room. Another specialty is a seafood platter that includes eight catches (about $12.50). Steak is available, if you're of a mind, for around $9. Appetizers include oysters in a variety of dishes, spinach salad and cold soup. Fortunately, they don't try to bore you into a coma by extending the country-inn bit to include mushy, mealy pate that passes for spoonbread, or other cornball dishes.

Expect to spend $30 to $40 for dinner, if you enjoy a moderate wine with your meal. For breakfast, plan on an extra $10 or so for bacon or ham and eggs with Bran'nola toast.

After breakfast, you can hop the little ferry, with your car, for the 10-minute ride to St. Michaels Island, where fishing and oystering make the excitement. But it's also very pretty, so you can just sightsee.

Now back to specifics in the abduction plan: Make plans early. Call the innkeepers, secure a date. Next call your intended and alert him, as casually as possible, that you're planning a suprise for him on that date. Make it sound mundane - like a Friday-night movie and dinner.

Don't tell a soul - except maybe a babysitter or neighbor. Alert his secretary that he'll be leaving after work that date, so she can push through any niggling business that may lurk in the back of his mind and could mar the trip. After all, he can't have fun if he was planning to spend Saturday morning on the final brief for court on Monday.

If you plan it for a weekend, begin with an innocent-sounding drink, having him meet you Friday, say somewhere downtown, around Connecticut and K. Clear any home projects a few days beforehand. Pay and bills that came with a pink slip.

Tune up the car. Pack it with spare everything he likes to keep. Tires. Spark plugs, Fans belts. Highway safety kit. (He always does these things, doesn't he?) Get road-maps that show your way clearly. Go to the bank and get a handful of cash - about $200 if you really want to be safe for two days. Or traveler's checks. Or credit cards - they spend like money at most hideaways - but check first.

You meet him downtown, take him to one of the little bars nearby. Have a drink. Toast your continued good times. Get in the car. Jump behind the wheel. (This is tour surprise, remember?) CAPTION: Picture, THE ROBERT MORRIS INN, ON THE TRED AVON AT OXFORD, MARYLAND.