In the monastery of San Giorgio in Alga, which is located in the Venetian lagoon, in 1943 the Nazis set up a secret military base. No one knows exactly what is happening there - officially it is a hospital. But the locals living in the vicinity of the lagoon are afraid of the night shadows that appear at night from the sea.
It seems that Tanya can finally forget about her criminal past - she is going to marry Volodya. He also loves her dearly, and together they make plans for a happy life. But unexpectedly, Volodya goes to a meeting and disappears. Tanya is desperate. Looking for her beloved, she finds her father and learns the terrible truth of the Akkerman fortress.