CROSSING BY NIGHT

Grand espionage-adventure at the dawn of WW II, with the lovely wrinkle that the spy is a woman: American-born Elizabeth Pack, whose real-life exploits on behalf of the British take on stirring fictional form courtesy of Aaron (Agent of Influence, 1988, etc.) It's unclear how close Aaron sticks to the facts: One doubts that the real Elizabeth Pack found herself locked in a dungeon, forced to whip a naked Polish foreign minister as he begged, ``Be cruel to me!'' But no matter. There's historical ambience to spare here, starting in 1935, when Elizabeth—the pregnant, spunky young wife of British diplomat Arthur Pack—attends a dinner thrown by Vita Sackville-West and hears Winston Churchill warn of global conflict to come. After Arthur—fearing disgrace because Elizabeth became pregnant before they married—gives up their newborn for adoption, Elizabeth plunges into the bloody cusp of current affairs, accompanying Arthur to Spain and tending the wounded on both sides of the Civil War. There, she falls in love with a Spanish diplomat and daringly rescues him from prison—a feat noted by British spymaster William ``Intrepid'' Stephenson, who recruits her to ferret out Polish advances in cracking the Nazi coding machine known as ``Enigma.'' In Warsaw, Elizabeth beds and falls for a Polish count, whom she turns, garnering much spy-data. She returns to England in triumph, only to be asked by Churchill to go back to Poland to steal a new-model Enigma. Hence the rendezvous with the Polish foreign minister, who in thanks for her strong wrist gives her an Enigma. In an extended, white-knuckle climax, Elizabeth smuggles the machine by train through Germany; dinner with a grateful King George VI follows. Great fun, featuring one of the strongest, most appealing heroines in recent thrillerdom. Aaron's best yet.