The story of The Mermaid: Lake of the Dead follows a seemingly ordinary young couple, Roman and Marina, whose peaceful life is suddenly overturned by a supernatural encounter. Roman, preparing for his wedding and enjoying his final days of bachelor freedom, goes on a trip with friends to a remote lakeside cabin. What begins as a harmless getaway quickly turns into a nightmare when he is mysteriously lured into the water by a ghostly, beautiful woman who appears from the depths of the lake.

After this strange incident, Roman returns home, but he is no longer the same. He starts experiencing disturbing visions, strange dreams, and a growing emotional distance that Marina cannot ignore. The seductive spirit he encountered—an undead mermaid bound to the lake—has marked him, tying his life to hers. As days pass, Roman becomes weaker, psychologically drained, and increasingly obsessed with the supernatural presence calling out to him. Marina, frightened yet determined, senses that another woman is trying to take her fiancé away, though she does not yet understand that the threat is not human.

Desperate to save Roman, Marina begins investigating the history of the lake and the origin of the cursed mermaid. She eventually discovers the tragic backstory: the mermaid was once a young woman betrayed and drowned by her lover centuries ago. Consumed by heartbreak, her spirit transformed into a creature driven by jealousy, longing, and vengeance. Each time she appears to a man, she enchants him, drains his life, and drags him into her cold underwater world, leaving their real-life partners devastated.

As Roman’s condition worsens, Marina realizes that the mermaid will not stop until she claims him completely. Marina seeks help from Roman’s ex-girlfriend, who has encountered the creature before, and the two women join forces despite their emotional history. Together they confront the supernatural danger, racing against time to break the curse before Roman becomes the mermaid’s next eternal captive.

The final confrontation takes place at the lake itself, where Marina bravely faces the mermaid, risking her own life to free Roman from the spirit’s grasp. Through courage and emotional strength, Marina manages to sever the mermaid’s hold, forcing the vengeful spirit to retreat back into the depths. Roman awakens, finally freed, though shaken by the ordeal.

The film ends with the couple reunited but forever changed by their brush with the supernatural. The lake remains quiet once more, yet the haunting presence beneath its surface reminds viewers that some tragedies never truly disappear.