Watch Les Visiteurs

After saving the life of King Louis VI, Count Godefroy is made the Count of Montmirail and promised the hand of Frénégonde de Pouille. However, as Godefroy heads to Montmirail, he is drugged after a witch secretly poisoned his flask. Godefroy hallucinates that his future father-in-law is a rampaging bear and puts him down with a crossbow bolt. During the subsequent funeral, Godefroy's servant, Jacquouille swipes the Duke's jewelry.

Godefroy beseeches a wizard to send him back in time, preventing the Duke's death. He agrees but bungles the potion, sending Godefroy and Jacquouille to 1993. The two quickly get into trouble with the police, with Godefroy being sent to a sanitarium after police believe him an amnesiac. After Godefroy tries destroying a postal vehicle, believing it to an infernal chariot, Godefroy and Jacquouille encounter Béatrice, an aristocratic beauty and dead ringer for Frénégonde due to being her descendant. Jacquouille also befriends Ginette, a pretty drifter.

Béatrice believes Godefroy to be her distant cousin Hubert and brings the two men to her home, leading to humorous reactions regarding modern devices like toothpaste. Eventually, Beatrice notices the Godefroy's seal and believes he stole the gem from Montmirail castle, now a hotel. When the group heads to the hotel, Jacques-Henri Jacquard appears as both the owner and descendant of Jacquouille. Godefroy's jewel begins to burn hotter as they near the castle, present-day location of the seal, eventually exploding and destroying Jacque-Henri's new car.

Godefroy purchases a night at the hotel, taking a secret passage only he was aware of. Inside, he discovers a letter which leads him to Eusebius' last descendant, Ferdinand. Ferdinand gives Godefroy the correct potion for his original desire, but learns that Jacquouille enjoys the modern world. Godefroy resorts to physically forcing his servant to return to the hotel with him.

While Godefroy talks with Béatrice, Jacquouille switches jackets and places with Jacques-Henri, changing the lighting, curtains, and bedding so that the potion allows Godefroy to prevent the Duke's death and strands Jacques-Henri in the past as Godefroy's servant.