The book "Diary of Mrs. R. S. Hermon, kept at Lucknow during May-December 1857" by Maria Hermon is a unique document reflecting the events that took place during the Indian Rebellion of 1857-1858. In her diary, Mrs. Hermon describes in detail life in the besieged Lucknow, the events of the military operations, as well as her own impressions and emotions. This document helps to better understand the complexity and importance of those events for India and the British Empire, and also reveals the author's inner world under conditions of stress and threat. Noted by literary scholars as an important source for the study of the history of the time, this diary remains an important testimony to the events that changed the history of India.