Galdós tells the adventures of the beautiful and poor girl Isidora Rufete, that because of the lies told by her father believes belong to a noble family and start a lawsuit to obtain recognition of their rights. His conviction that makes you develop a noble aristocratic pride that leads her to drop out of what could have been a modest life more or less happy: boyfriend rejects as a doctor with a good future career, it is unable to work and acquire habits life very expensive to maintain and falls for a ruined marquis that will bring. money and will continually pregnant with a son she never qurerrá recognize. So as not to relent in their aspirations and while litigation is pending, is forced to bail out by becoming the mistress of men in good standing. The aristocratic family that believes belong to counterbalance its turn denouncing demand for forgery of some documents (which made his father) and Isidora gives his bones in prison. Finally, to convince a notary public that there is nothing noble and that his father played a trick waived his claim and leave prison. But it is unable to live modestly and seeing that no other solution to keep your train of life, is thrown into prostitution. Isidora's character is not without its grandeur, constantly refusing to settle for compromises, not detenrse at nothing in their hope to reach the site "rightful." That hope, which has grown with it, has shaped his character, his personality, so indispensable and needs to be realized.

The character of the Marquis de Joaquín Pez, the trickster, frivolous and ungrateful skull is the only man I really want to Isidora despite his constant abuse is a clear precedent for Juanito Santa Cruz and its story of love and impossibilities is very similar to which he will live with Fortunata. In addition, we presented a long gallery of interesting effects, such as the realistic and ordinary aunt Isidora, the Leecher, or his uncle, Joseph of Relimpio, as faithful as useless, which paints a naturalist Galdós sinking in alcohol; Juan Catalan Socialist Bou lithographer, opinions quite advanced and caricatured by the moderate Galdós, or the doctor Augusto Miquis, which is to be the positive part of the work to embody the prosperity due to good sense and his own efforts. Least made the most miserable seem especially Isidora's brother, Mariano, to which we are depicted as an incorrigible criminal who just carry out an attack against the king anarchist.
Along with the usual wit in the language and easy to transmit environments and characters in this novel stand out (besides the courage to start in untrodden paths, at least in Spain a) the interesting recollections of the psychiatric care of the time ( with despcripción of Isidora's father stay in Leganés) or social trends of the moment (from cars to walk down the Castellana to the games and fights child offenders in the south of Madrid).
Is missing, as is usual in Galdós, clarity of purpose and a greater importance than we are told. Galdós brings up, as in
Fortunata and Jacinta, current political events that seem to want to relate to the adventures of the characters, although it is difficult to determine
how. In the lesson, which includes claims to want to understand the turbulent history of Isidora that everyone should learn to take their place and in any case, way up by merit rather than waiting for a miraculous good fortune. However, as the character got Isidora is that faith that seeks what he believes his and the tragic impossibility of going back that she feels constantly.