Maribel is a lady of the evening in the Madrid of the late fifties. One night, she meets Marcelino, a shy and quiet man who falls for her without realizing, apparently, of her condition of prostitute. To Maribel he is just a client, at the beginning, but gradually she begins to feel attracted by the provincial and shy owner of a chocolate factory in Soria. Pili, Rufi and Nini, Maribel’s colleagues,  evil-minded by nature, begin to suspect of this relationship and they think that the chocolate maker could be a murderer. When Marcelino proposes to Marible, they decide to intervene and dispel Marcelino and and his 'strange family' from Maribel.