Thirteen Years Later (Danilov Quintet #2) by Jasper Kent

Description

1825, Europe and Russia have been at peace for a decade. Bonaparte is long dead and the threat of invasion is no more. For Colonel Aleksei Ivanovich Danilov, life is peaceful.

Then, Aleksei once again ends up in the thick of things. Russia, although at peace with Europe, has internal conflict to be resolved. The Tsar is not popular and secret societies are gathering and plotting to overthrow him. On top of that the Tsar has another enemy, an unknown entity, who wants revenge. Aleksei is once again undertaking the role as a spy and trying to protect the Tsar although it isn’t easy with all the secrecy involved.