At no point during their initial "appointment" does she realize she isn't talking to an analyst, and he sees nothing immediately abnormal either. "My tax clients often unload their love lives," he says. Once he realizes Anna's mistake, he's still too wishy-washy to come clean, worried that he'll hurt her feelings.
The mechanics of this premise are a bit much to swallow at first. Anna turns out to have a dyslexia-like disorder that gives her trouble with counting and orientation, which is why she goes into the wrong office in the first place. Once there, however, her confusion is maintained in part because William is one of the only tax lawyers in the world to have a psychiatrist's couch opposite his desk. And then, Anna's first two "sessions" are both remarkably short and lacking in any kind of conversational pauses that would allow William to explain himself. Leconte downplays much of this, but it's never entirely clear if the details of the setup are meant to be a deliberate spoof or a hastily plotted way to set the story in motion.
In an American film, wacky mistaken-identity antics would most likely ensue, possibly with incompetent mobsters becoming involved somehow, but the focus here is on the relationship between the two leads -- although a dangerous peripheral figure does indeed show up in time to set up a climactic emotional conflict.
Anna is no ordinary neurotic: Her husband (Gilbert Melki), injured in a car accident, will no longer have sex with her, but, in the vein of Lars von Trier's Breaking the Waves, he encourages her to have affairs and give him the play-by-play details when she returns home. There's more to the story than that, though; as Anna opens up, she lets slip certain things that cast events in a different light. Assuming, of course, that she's telling the truth.
William has issues of his own. Recently separated from a librarian named Jeanne (Anne Brochet), he still confides in her and allows her to exert undue influence upon him. Though amiable on the surface, Jeanne seems to take pleasure in showing off her newest man (Laurent Gamelon), even as she engages in a bout of "off the cuff" casual sex with her ex. William's not exactly the poster boy for confident masculinity (check out the apron he wears while cooking dinner!), and having Jeanne's sexually active new life flaunted at him on one side and Anna's sexual hang-ups on the other is more than he can bear. So what else is there to do but start seeing the psychiatrist that Anna was trying to go to in the first place? Ostensibly he's there to ask for pointers so that he doesn't mess with Anna's head too badly, but in truth a little therapy is just what he needs.
Would it surprise you terribly to learn that William starts to fall for Anna? The real shrink (Michel Duchaussoy) mentions that female sexual pleasure is frightening for men, turning them back into scared little schoolboys, but Leconte and screenwriter Jerome Tonnaire (Bon Voyage) also skillfully display the degree to which the female exuding sexuality can wield it in devastating fashion without even consciously realizing the effect on nearby males. Anna might in fact be coming on to William, or she could just be looking for a friendly ear; what she doesn't realize is that the majority of men have trouble telling the difference, especially if they haven't been trained as psychiatrists (guys, raise your hand if you can relate).
Foreign-language movies that reach the U.S. often feature merely adequate subtitle translations, and occasionally even ludicrous ones, so let's hear it for translator Nigel Palmer, who has managed to interpret Tonnaire's words while maintaining several cleverly crass turns of phrase that can't possibly be the same in French, but are likely analogous. For example, when William mentions to the real psychiatrist that he just wants to contact Anna, the doc rejoins that what he really means is he wants "cunt-act." Later lines of dialogue like "Dump her or hump her!" follow along those lines. It's always nice when you get a knowledgeable linguist who follows the spirit of the dialogue rather than the letter of it.