"It [the Orient Express] lends itself to romance, my friend. All around us are people, of all classes, of all nationalities, of all ages. For three days these people, these strangers to one another are brought together. They sleep and eat under one roof. They cannot get away from each other. At the end of three days they part. They go their several ways, never, perhaps, to see each other again."

Agatha Christie

The Orient Express, the most exotic, romantic, luxurious train ever to thunder across a continent, is back on the rails again. Once ridden by royalty, adventurers, statesmen and spies: immortalized by Agatha Christie's "Murder of the Orient Express: and finally done in itself by modern jet travel, the legendary "king of trains and train of kings" has been revived by a Swiss tour firm. Its recent run to Istanbul launched a season of sentimentally that will include trips to Athens and Baghdad.

As the vintage, deep blue-and-gold coaches of the Nostalgic Orient Express - seven mahogany-paneled sleepers, two plush Pullman parlor cars, a red-up-holstered diner and eight-stall shower car - pulled out of the Zurich station, brown-uniformed conductors in smart pull-box caps placed crystal vases of fresh-cut flowers in mirrored niches at each end of the sleeping cars. And as the train picked up speed through the suburbs, waiters wearing white, starched jackets trimmed with gold braid moved along the corridors shouting "Aperitif."

The 90 passengers, who paid over $1,000 each for the two-day, 1,200-mile train ride, Istanbul sightseeing weekend and return jet flight to Europe, sipped Negroni cocktails as the express sped through the vest-pocket state of Leichtenstein, across the Rhine and over the Austrian Alps. Later, clad in evening wear, as the train rattled through the night, they dined by candlelight on creme a la reine, saumon en belleue and cuissot de veau, pausing briefly midway through Alaska souffle to have their passports stamped by customs officers who boarded at the Yugoslav border.

Next day, as Nis, the coaches were hitched up to an old black steam locomotive, and belching clouds of grey coal smoke set off across the Balkans. At Sofia, capital of Bulgaria, passengers were entertained on the station platform by folk dancers, and the next morning welcomed to Turkey by a local brass band.

The man who staged the nostalgic extravaganza is Swiss train buff-entrepreneur Albert Glatt, director of the Zurich-based Intraflug AG charter flight agency. When the daily Paris-Istanbul Orient Express was canceled in May of 1977 because it could no longer compete with the jet, Glatt bought and restored some of the iriginal rolling stock. His antique train includes luxury, eight-compartment sleeping carriages built in 1929: 50-year-old Cote d, Azur salon coaches decorated with carved glass nudes by Rene Lalique, and a carpeted diner with still-functioning coal-fired cooking range.

Railroading into the past was an instant success, and the six long-distance runs scheduled this year - including trips to Istanbul and Athens reserved solely for Americans, and an 11-day marathon to Baghdad - are already fully booked. Between long trips, Glatt hires out his special for company outings, anniversaries and birthday parties.

The first Orient Express left Paris on Oct. 4, 1883, the outcome of a shattered loved affair. It was created by a young Belgian engineer named Georges Nagelmackers, whose father sent him to America to recover from a broken heart. There, he met George Mortimer Pullman, architect of a luxury long-distance rail travel, and, inspired by him, returned to Europe to found La Campagnie International des wagons-lits.

Naglemackers' inaugural "Express d, Orient" - six sleeping cars and a diner - took 40 passengers via Munich, Vienna and Bucharest to the Bulgarian Black Sea coast, from where they proceeded to Istanbul by overnight ferry. Later, a direct service was established to Istanbul, with onward connections from the Asian shore of the Bosphorus Straits to Damascus and Baghdad.

The first Orient set new standards in speed - thundering along at as much as 45 miles an hour - and comfort - passengers slept on embroidered percale in separate compartments, unlike American cars which had a corridor and curtains and dined on eight-course meals served by waiters in knee breeches, white stockings and buckled shoes.

Recalling the train's heyday, conductor Maurice Barillot, 37-year-old Parisian with 15 years experience aboard Wagons-Lits sleeping cars, said nostalgically, "It was a great way to travel . . . if you had the time."

Early passengers included Ottoman Sultan Abdul Hamid. He traveled with his harem and no ticket collector dared check the carriage specially hired for his wives. King Leopold of Belgium was a regular traveler, and Paris dancer Cleo de Merode was such a frequent guest on his royal sleeping car that it was nicknamed "Cleopold."

King Boris of Bulgaria loved the Orient Express. He would commandeer the driving seat, sending chandellers swaying and champagne spilling as he raced the train across his Balkan kingdom. Arms dealer Basil Zaharoff, the "King of Cannon Manufacturers," international cabaret star Josephine Baker and King's Messengers used the Orients to commute between capitals. A retired Austrian officer who took a disliking to the train once tried to blow it up, and once it was marooned for a week in Turkey by a snow storm.

This incident probably provided the inspiration for Agatha Christie's famous whodunit, in which villainous Samuel Ratchett was murdered by fellow passengers whilst the Orient Express was stuck in a Serbian snow-drift. Other writers - Graham Greene ("Istamboul Train") and Maurice Dekobra ("Madonna of the Sleeping Cars") - embroidered the legend, and Ian Fleming ("From Russia With Love") brought it to the cinema screen.

But slowly the glamor grew thin as the rich and famous took to air travel. Students and migrant workers took their place. Gradually the Orient Express' elegant trappings were removed, and on the final journey passengers had to bring along their own blankets and food.

As one French official put it: "No one wants to sit up for three nights and two days if they can help it."

But like an aging actress reluctant to make her last bow, the train favored and glamorized for nearly a century by aristorcrats, novelists and millionaires is making a comeback. And although her performances are no longer daily, sentimentalists can still travel the Nostalgic Orient Express several times a year.