«Mentor in Christ» — a religious-psychological novel about the clash of living faith with church formalism, where alongside the elderly Cardinal Felix Bonpre appears a boy, and the familiar order begins to crack under the pressure of foreign conscience, fear, and hope for forgiveness. For Marie Corelli, this is not a private drama, but a grand story about the end of the 19th century, when religious institutions were losing moral authority, and society increasingly chose external piety over internal honesty. The book concludes the «Religious Trilogy», which also includes «Barabbas» and «The Sorrows of Satan», but is connected to them not by a common plot, but by a circle of themes: fall, temptation, repentance, and the possibility of salvation. Here, not only miracles and accusations are important, but also the very setting — Rouen, church circles, aristocratic environment, debates about faith, duty, and the right to judge another.
After the meeting of the cardinal with the homeless Manuel, events begin to unfold around them, which some consider a sign from above, while others — a dangerous challenge to established authority. Healings of the sick, revelations of crimes, and the growing attention to the boy turn a private story of mercy into an open conflict with the church system. Against this backdrop, several interconnected storylines develop: the fate of the artist Angela Sovrani and Florian Varillo, the story of Sylvie Hermenshtein and reformer Aubrey Lee, the debates of Abbot Verniot and socialist Guy Grandy. All these lines converge on one question: what is more important for a person — adherence to the canon, public reputation, or fidelity to one's own conscience.