Autumn 1944 in Tallinn, Estonia. German forces retreat as the Russian army settles in. Young soldier Aleksei is sent from the frontline to work in a prison filled with Estonian political prisoners.

When a nun in a remote convent claims immaculate conception, the Vatican sends a team of priests to investigate, concerned about an ancient prophecy that a woman will give birth to twin boys: one the Messiah, the other the Antichrist.