The Four Musketeers head to Russia to retrieve the royal Psalms stolen by one of the Revolutionary Brethren.

The Four Musketeers pursue Vorontsov until he finally arrives in St. Petersburg. Here D’Eon attempts to gain permission from Empress Elizabeta to operate in Russia.

Following the Empress’ death, Pyotr has become Emperor of Russia. Ekaterina, the woman who warned the Four Musketeers, steals the throne back from him with their help. The Four Musketeers continue to battle members of the Revolutionary Brethren.

D’Eon’s battle against Vorontsov is finally finished, with Lia dealing the final blow. The Four Musketeers follow Robespierre to London.

After D’Eon speaks to the Queen about two souls existing together in one vessel and Durand is released, the Four Musketeers head for Medmenham Abbey.