Sebastian appears to be a seducer most famous for his unscrupulousness at the highschool. For a Don Juan like him, Kathryns (who is his attractive stepsister) offer that she makes for him in summer holidays seems to be too easy: To seduce and make a hussy the new girlfriend Cecile of her ex-boyfriend. Sebastian has a better idea and offers to his stepsister a bet: Up to the end of summer holidays he would have seduced Annette, the highschool principals daughter who has recently made a vow of chastity. Casually he would have managed the thing with Cecile. If he wins, he gets a night with his stepsister Kathryn, the only woman he could not seduce so far. If he loses, he must leave his valuable Jaguar Oldtimer Cabrio to her. But then everything comes different...