The research covers the history of Inquisition from its establishment till the times contemporary for the author. In his book G. puts a special attention at the activity of the Order of Dominicans in the context of the Inquisition, including the persecution of some branches of the order itself, such as Observants. The author took 1230-s as the time of shaping the Inquisition as a special institution; in 1233, it was given under the surveillance of Dominicans. The nest step was made in 1252, when Pope Innocentius IV published his bulla officially creating Inquisitional tribunals and giving permission for tortures.

The author describes the activity of inquisitors assigned by the pope, as well as the functioning of their chancellery, and certain types of duties. For instance, a notary had a spiritual rank and fixed testimonies of the accused and the witnesses with his personal sign. Important positions in the system were taken by a procurator, a doctor, and an executioner. In his book G. analyzes the process of the tribunal, as it was: how an accusation was formed, how an interrogation was hold, what punishments did they use.

The author observed the activity of the Inquisition through several centuries, including not only the struggle against heresies and their dissemination, but also the organization of the witches processes, and the deeds of the Inquisition in the New World, accenting the fact that by the sixteenth century inquisitors were mainly high hierarchs, not brethren of the Order of Dominicans.

He put a special attention at the activity of the Inquisition in the epochs of the Reformation and the Enlightenment, telling about some processes against researchers, and mentioning a participation of Jesuits in those trials. As for the later history, G. made some essays on the events of the nineteenth century connected with the Risorgimento movement in Italy. Through all the work, he gives a negative assessment to the Inquisition and to the Papacy supporting it.