Biochemist Paul (Tate Donovan) has no luck at all with women and is persuaded by his friends to visit a fortune-teller, who gives him a love potion no. 8 to make him irresistible to women. Being a scientist Paul believes none of this until his cat accidentally gets a taste and attracts every female cat in the neighbourhood. He enlists fellow scientist Diane (Sandra Bullock) to help him analyze it, and after experimenting on monkeys, they decide to test it on themselves and both embark on a quest to find romance. In the end, they discover that they really want each other; but before they can get married, an old boyfriend of Diane's returns with his own dose of love potion number 8. Paul's only hope is to get something even more powerful. Love Potion no. 9.