St. Petersburg, 1829. The city is shaken by a string of suicides and unfortunate accidents: Count Ukhtomsky shot himself, Lieutenant Repetin broke his neck after falling from a horse, and Baron Baumgarten was found hanging. The police attribute everything to a random coincidence of circumstances, but the coroner, Ilya Andreevich Tonner, thinks otherwise. He manages to discover a highly interesting detail: a lady is involved in the case—her face hidden under a veil. Tonner is sure that the woman knows many secrets, including the riddles behind the murders…