Women spies--often notoriously glamorous and driven as much by the thrills as the cause--have customarily used seduction to get what they want. Betty Pack, the subject of this latest biography by Lovell (The Sound of Wings, 1989; Straight on Till Morning, 1987), was a typical woman spy. Not so typical, though, was the significance of her accomplishment. Acknowledged as responsible for providing some of the most important British communications intelligence of WW II, the American-born Pack was a woman ""who took life as she found it, happily meeting challenge after challenge head-on, no matter what the consequences of the collision."" Described as the most beautiful debutante of the Washington season, she was married at 19 to Arthur Pack, a British diplomat who had impregnated her. The child's birth was kept a secret for many years as Pack, a ""dreadful parent,"" let her son be reared by a foster family in England. Her espionage activities began while stationed in Civil War Spain and continued when her husband was transferred to Poland, where she seduced a top-ranking Pole from whom she learned details of the German Enigma code-machine. Her most significant triumphs, though, came in Washington. There, she seduced and turned an Italian admiral, as well as a Vichy French diplomat from whom she obtained ciphers that gave the Allies vital information about enemy movements. Loyal but unreflective, Pack had methods that were daring and unorthodox--her after-hours nude appearance at the French Embassy so stunned a suspicious nightwatchman that he fled, facilitating the opening of the safe holding the ciphers. Pack's life in France after the war was poignantly anticlimactic; she began writing her memoirs, but died in 1963 from cancer before they were complete. Solid research and tribute paid where due, though Pack, despite all the glamorous and daring things she did, and despite Lovell's best efforts, never quite comes alive here. Disappointing.