Marcel will inherit one million francs—on his wedding day. Unwilling to give up his bachelorhood, but in dire need of cash, he persuades Amélie, a coquette and his friend's mistress, to act as his fiancée. The pair of friends are embroiled in a moral dilemma after accidentally spending the night together.

What should be the reaction of a wife who receives a parcel in the morning mail from the In and Out Hotel... containing her husband's braces? And what is the In and Out Hotel?