Knock, a retired crook-turned-qualified doctor, arrives in the small village of St-Maurice to implement a "method" he believes will make him rich: he will persuade the villagers that healthy people are simply people who don't realize they are ill. To do this, he needs to find an illness (be that real or imaginary) that afflicts each person. An expert in the art of seduction and manipulation, Knock comes close to achieving his goal. But his plans are rattled by two things he had not foreseen: his own romantic feelings and the appearance of a dubious character from his past who has come to blackmail him.