British first-novelist Austen makes a steadily involving, if finally disappointing, little thriller out of a familiar plot idea: a mysterious man hires a woman to recreate an episode from his past. The woman in this case is young, halfhearted prostitute Shirley, who narrates--first filling in her drab middle-class past (her hated, puritanical father, her barely intentional drift into prostitution) and then reconstructing her encounters with enigmatic Paul Fox . . . which begin when Shirley answers an ad (in a sleazy mag) for a ""model"" with acting ability. What does Fox want Shirley to do? Well, along with large checks, he periodically sends her ""scripts"" to memorize, detailed little plays in which Shirley plays a London acting student named Juliet; and ""Juliet"" is to meet Paul Fox in a series of supposedly chance encounters--on a train from Brighton, at the Tate, in a bar, in the park. No sex. No kinkiness. Just an edgy, timid romance between a rather brash young woman and a mild-mannered middle-aged fellow--which is what silver-haired Fox turns out to be. But Shirley has her ups and downs with these bizarre performances: she forgets her lines, she drops out of character (sending Fox into a fury). And, predictably, she becomes involved, unable to end the set-up even when it threatens to turn sour--or dangerous. Finally, then, the affair reaches its inevitable conclusion (graphic consummation at a hotel); Shirley isn't sure how much her love is an act, how much is real; and Fox at last drops the playacting to explain just who ""Juliet"" really was--and why he has gone to such absurd lengths to recapture their relationship. True, Shirley's identity crises along the way are clichÃ‰d stuff, emphasizing the whole story's similarity to a number of '60s/'70s films in the British/European/Hitchcock mode. The explanatory windup, too, is a let-down. But Shirley is a brisk, somewhat unpredictable narrator--and the minute detailing of her ragged performances gives this essentially dark tale a bright, ironic tilt which is often highly engaging.