Philippe Lambert, an attractive young attaché to the Prime Minister's office, is a man of many female conquests. One of them, Madame Grandbourg, wife of a very influential man, sent him a passionate letter, which he lost at the theater. Marion, the usherette who found it, contacts him to ask him for a "favor" in exchange for its return: to avoid eviction from the family apartment, because of the father, who gardens in every room and constantly floods the downstairs neighbors. At first, Lambert refuses to give in to the "blackmail" and calls in the police to unmask the indelicate woman, but love soon gets in the way...