The spirit of Halloween presided over the second session of Game 7 in the world chess championship yesterday in Seville, Spain. Like children out for tricks or treats, defending champion Gary Kasparov and challenger Anatoly Karpov scared one another for nearly 40 moves before agreeing to a 79-move draw.

In the first 41 moves, played on Friday, Kasparov had let his king be crowded dangerously into a corner. But yesterday, he pulled off an escape worthy of Harry Houdini.

In the game's first session, Kasparov avoided exchanging queens; with his king boxed in a corner, he would have had trouble defending his pawns on the other side of the board. But to make any progress, Karpov had to set the black king free, so Kasparov was able to exchange queens and move his king over to defend the pawns.

For a while, after move 59, the situation was deadlocked with the white king blocked by black's e-pawn and bishop, and there was a sort of dance with nobody knowing who was leading. Karpov threatened the black h-pawn, but could not take it without allowing Kasparov to advance his b-pawn, clearing the way to make a new queen.

Finally, Kasparov made his break, and three black pawns died so that the fourth could reach the throne. Karpov made his queen one move after Kasparov and remained a pawn ahead in the final position. But Kasparov's king was too active, and he could have gone into a theoretically drawn pawn end game after 80. Qf2ch, Qxf2ch 81. Kxf2, Kf4. Karpov, uninterested in demonstrating this possibility, accepted the draw.

Game 7 of this match may prove to be the most important of the championship. It may depress Karpov not to have won a game he was very close to winning, and it may give Kasparov momentum for Game 8, Monday, when he will have white.

Grandmaster Lubomir Kavalek contributed to this report.