Deputy Commissioner Monika Gniewosz must break with her past and change her surroundings. So, she decides to move from Warsaw to the sleepy town of Pełnia, where life flows leisurely and the residents believe that the spirit of a drowned woman haunts the lake. Monika begins working at the station and is called to the scene of an attack on a young man on her very first day. Soon, she also learns about the disappearance of the innkeeper. Gradually, the affairs of the town draw the officer in like a dangerous swamp. In Pełnia, nothing is as it seems.