It is Paris at the turn of the century, and the lovely Raymonde Chandebise, after years of wedded bliss, begins to doubt the fidelity of her husband, Victor Emmanuel, who suddenly has become sexually inactive, or, as Raymonde puts it, “after having been a husband--and what a husband!--suddenly stopped--like that! Between one day and the next.” She does not realize, however, that his behavior is due to a nervous condition, and she begins to suspect that he has a mistress.
She confides her doubts to her old friend Lucienne, who suggests a little trick to test him. They write him a letter, in Lucienne’s handwriting, from a fictitious and anonymous admirer, requesting a rendezvous at the Hotel Coq d’Or, an establishment with a dubious reputation, but a large and prominent clientele. It is Raymonde’s intention to confront her husband there, and she and Lucienne leave to do so.
When Victor Emmanuel receives the letter, however, he has no interest in such an affair and believes the invitation from the mysterious woman was meant for his best friend Tournel, a handsome bachelor who, unknown to Victor Emmanuel, has his eye on Raymonde. Tournel, hot blooded and easily excited, quickly exits to make the appointment.
Meanwhile, Camille, the young nephew of Victor Emmanuel, is overjoyed to have a speech impediment corrected by a new silver palate from Dr. Finache. In celebration, he and the household cook, Antoinette, also hurry to the Hotel Coq d’Or, followed by Etienne, the jealous husband of Antoinette. Dr. Finache, also looking for a bit of fun, decides to go to the hotel in search of his own afternoon rendezvous.
To complicate the matter further, Victor Emmanuel, with the intention of sharing his amusement, shows the letter to Lucienne’s husband, Carlos Homenides de Histangua, a passionate and violent Spaniard. Carlos recognizes Lucienne’s handwriting and assumes that she is trying to start an affair with Victor Emmanuel. He runs off to the hotel vowing to kill her in revenge. Victor Emmanuel, hoping to prevent the threatened murder, hurries off in pursuit.
Feraillon, the proprietor of the Hotel Coq d’Or, runs his business with a military precision, which, alas, is about to be disrupted. Finache arrives looking for fun. Raymonde arrives looking for Victor Emmanuel. Tournel arrives looking for Raymonde. Camille arrives with Antoinette, followed by Etienne, who is looking for them both. Carlos arrives looking for Lucienne; and Victor Emmanuel, the most innocent of the entire group, arrives looking to stop Carlos.
The presence of all the people at the hotel causes further complications and misunderstandings. Carlos, attempting to shoot his wife, violently shoots at anything that moves. Victor Emmanuel sees Raymonde talking with Tournel and believes she is unfaithful. Mistaken for Poche, an alcoholic porter at the hotel, Victor Emmanuel is believed to be insane. And, to escalate the action even further, Camille loses his palate and Tournel tries incessantly to seduce Raymonde.
The confusion persists even after all are reunited again at Victor Emmanuel’s house. However, things begin to clear up when Carlo discovers on Raymonde’s desk a rough copy of the letter written by Lucienne, this one in Raymonde’s handwriting. Next the owner of the hotel comes by to return an article left behind by a member of the household and clears up the confusion between his porter and Victor Emmanuel.
Finally, Raymonde tells Victor Emmanuel the cause of her suspicions, and he assures her that he will put an end to her doubts--tonight.