In Game 4 of the world chess championship, Anatoly Karpov did what a rider is supposed to do after being thrown; he got right back on the horse.

Struggling to come back from his crushing defeat exactly a week earlier, Karpov, playing black, used the same variation of the same opening with which he had lost Game 2: the Zaitsev variation of the Ruy Lopez. Five hours later, after some unusual, complex and dramatic play, including the elimination of all his opponent's queenside pawns, he reached an adjourned position where he was inviting world champion Gary Kasparov to take a draw by perpetual check. Kasparov, who is supposed to be the adventurous player in this match, raised his eyebrows in surprise when Karpov steered the game into a different variation of the Zaitsev. Kasparov had arrived late at the Hotel Macklowe's Hudson Theatre in Manhattan and calmed down with some deep-breathing exercises before going into action.

Among those present for this game were two of the highest-ranking aristocrats of chess: former world champion Boris Spassky and grandmaster Victor Korchnoi, who defected from the Soviet Union and was Karpov's perennial opponent for the championship in the late 1970s and early '80s.

Karpov had played this same variation against Jan Timman in the final candidates' match in Kuala Lumpur, Malaysia, earlier this year. Kasparov departed from that game with yesterday's sharp 18. exf5. Timman had played 18. Rae3, and Karpov blocked the position with 18. ... f4.

On the 19th move yesterday, Karpov introduced a novelty by capturing a pawn with the bishop on d5. It is hard to understand why Karpov, obviously getting ready for this continuation, used almost a full hour to reach it. Did he want to lull Kasparov into a sense of security?

The position after 21. Bd2 has already been published -- in a theoretical article, not an actual game, with the evaluation that white has a strong initiative. The next few moves must have confused all the computers and the grandmasters at the scene, who were eagerly suggesting all kinds of moves. The real shocker came when Karpov played 22. ... Bf7 -- a surprise move that he might have prepared in advance in spite of the time he spent apparently pondering it. He could not play 22. ... Bxf3; 23. Rxf3, Qxb4 because white can safely play 24. Be4, (24. ... Rxe4; 25. Qd5ch wins the rook) and then infiltrate the black king's position via the weak white squares.

Now it was time for Kasparov to come up with something unusual. He put his rook on e6 where Karpov's bishop could take it, and Karpov by instinct captured a bishop rather than take the exchange. Why should he create deadly threats against his king on the white squares?

With 24. Rb3, the world champion sacrificed his last queenside pawn to get his pieces working together more effectively. He managed to pile up his rooks on the e-file, and the question was whether he could break through on the kingside. His queenside pawns had melted away and he gambled all he had to open the white diagonal leading to the black king. With 37. g3 (a quiet move of deep, subtle beauty), he was preparing to switch his knight via h4 to g6. That move must have been frustrating to Karpov, who was tied up and could move only his pawns.

Karpov got caught in front of his own pawns, unable to come to the king's defense. With 29. Qe2, Kasparov forced Karpov to take the exchange on e6. He might have tried the same maneuver one move earlier, but even as he played it the move was powerful enough to create unpleasant threats. When finally Karpov's queen came to the kingside, Kasparov was able to win Karpov's bishop.

Both players had been in time pressure, and Karpov's last moves made it clear that he would be happy to accept a draw by perpetual check. The game was adjourned in a position where Kasparov has such a possibility at hand. But he sealed his move with the idea of looking for a possible win.

What he finds in overnight analysis will be seen if the game resumes as scheduled at 5:30 p.m. today.

Lubomir Kavalek is a chess grandmaster. Joseph McLellan is a Washington Post staff writer.