Once every four years in the spring, when it's Mermaid Week, mermaids and mavkas, forest nymphs and dangerous mystical creatures, emerge from the Dark Lake, which is in fact a gateway to the Beyond, to hunt down people with filthy souls. In their minds, all people are good for nothing: they are traitors, liars, murderers, or thieves.

Over the course of six days, they capture such people one by one, drag them to the bottom of the Dark Lake, and their vital energy turns into energy for the mavkas and mermaids to feed on for the next 4 years. The power accumulated in those six days allows them to perform a ritual on the seventh day of the Mermaid Week - in the Short Night: they drag all the people who happen to be in the forest at that time to the Dark Lake, have enchanted them with the sound of the mavkas singing. Striking in their non-human beauty, the mermaids rule over the mavkas. They are purely demonic original creatures of the Beyond: they are in fact a high caste in the mystical world of the Dark Lake.

They keep the mavkas tied to them with invisible threads. Mavkas are the souls of drowned girls from different - decades. They have forgotten who they once were and what happened to them, and have therefore become vengeful, cruel tools in the hands of the

mermaids. They have beautiful, magical voices that can "bend" people's minds and warp their reality. Our Mavka goes out hunting for her prey, but on a path through the forest she accidentally falls under the wheels of an SUV. The driver, Lukian, a biology student who is camping in the woods as part of a science expedition, offers to take her to a doctor, but she refuses and stays with him in the camp, exhausted. While Lukian's friends are trying to figure out how to help her, Mavka heals herself, keeping a wary eye on Lukian.

She is convinced he gives off the smell of a woman's tears, so he must have wronged his beloved, and Mavka decides to come back for him later. Lukian indeed does have a complicated relationship with his already ex-girlfriend Khrystyna, his fellow student, who immediately becomes jealous of the weird stranger. But Mavka and Lukian suddenly find they are falling for each other: Mavka fails to "bend" Lukian's mind despite making two attempts, and the more they talk, the more Maka comes to admire him. She marvels at his efforts to protect the forest from hunters.

He shows her the glorious beauty of nature, which Mavka had forgotten how to see. She had also forgotten how to do good. The insidious plans of the mermaids, who feel threatened by the young man, prevent the two of them from becoming truly close. Mavka is also held back by her dark side, that of a forest creature from the Beyond, which still has power over her. In the end, passion takes a hold of them both, and Mavka is willing to surrender to love. Having already learned about her mystical origins, Lukian is willing to love Mavka as she is.

But the mermaids intervene - and so too does Khrystyna. She turns into a mavka herself and seduces Lukian by playing tricks on his mind. On the Short Night, the mermaids hole a great feast in the forest of a kind never seen before, and the folks “'invited” find themselves under the sway of the forest's demonic forces. Mavka learns of Lukian's "betrayal", but she does not seek revenge: on the contrary, she feels pain, just as she had done in her past life.

She heads to the Dark Lake, because she wants to spend the rest of eternity in the Beyond. But at the bottom of it, she feels someone reach out and touch her. It is Lukian! He manages to get to her and save his beloved, and Mavka gets a second chance to live among people.