Stef, an adventurer and collector of unusual things, buys an old army flask at an underground auction. This spontaneous purchase begins an investigation that leads him to a remote village on the edge of a huge swamp. Local residents still believe that deadly creatures live in the swamp, and that the ancient fish Mar lives in its dark waters. No one ever stays in the swamp after sunset. No one ever opens the door to those who come in the night. Because night is the time of Marie and her monstrous creatures. But in order to solve the mystery of the distant past, Steph needs to become someone who is not afraid to take risks in the present.