Lena and the children resurface in an underground lake where they find Ada. Guided by Ilse's spirit, the small group enters the world of the Vrill. Meanwhile, Marta's henchmen, revolted by her extremism and unethical methods, kill her. Refusing to admit that Lena allowed herself and the children to sink into the surface lake, Rafal follows their trail to the underground lake and finds them. However, he can only save the children at the cost of a terrible sacrifice...

When Lena returns to Ilse's house, her grandmother's spirit takes control of her own. Meanwhile, Marta discovers an underground lake that leads to a parallel reality, the perfect world of the Vrill. The energy emanating from this world can grant immortality and eternal health. Ilse's spirit guides the two children Marta is holding out of the sanatorium and back to Lena. Together, they head to a nearby lake before jumping into the water...

Two of the missing children are intercepted by Marta, who takes them to a room within her Black Daisies sanatorium. Lena manages to sneak into the facility's secret wing, where she discovers information about Nazi experiments during World War II, including those conducted by a mad scientist who wanted to create a new race of human beings using the women of Walbrzych as guinea pigs. She also discovers that Ilse was her grandmother...

While exploring the underground tunnels alone, Lena stumbles upon the former Nazi laboratory. There, she discovers CCTV footage showing Ada and children who disappeared from the same laboratory. Marta, for her part, maneuvers to have the investigation taken away from Rafal. The young police officer then reveals to his boss that his father committed suicide after participating in the restructuring project of a local mine run by Marta's husband. Rafal then gives Lena a video filmed on the fateful day she was taken away from her daughter Ada. Horrified, she sees herself trying to drown Ada. Marta then discovers that Lena knows about the secret laboratory where she conducts secret experiments...

Lena discovers that the key Sznirel gave her is to a house that belonged to a nurse named Ilse. At the entrance to the house, she comes across a box containing a bandana with the symbol of the Vril, a secret society dating back to the time when the Nazis were conducting experiments. Rafal, shocked by the death of his lover's father, killed by the police, accuses Maria of hiding dark secrets under the guise of philanthropy. The police continue to search the underground tunnels and approach very close to where Ada and the children are, without hearing the teenager's screams...

Ada and the missing children wake up in an underground tunnel, with no memory of what happened to them. While the police are interested in the Nazi treasure trail, another child goes missing, angering the locals, who believe the kidnappers are Roma. The police then raid their community, during which Luca's father is killed. Meanwhile, Lena continues her search, which leads her to a forest near Walbrzych. There she meets a strange homeless man, Sznirel, who mistakes her for a certain Ilse and gives her a mysterious key...

Convinced of her daughter's innocence, Lena conducts her own research and is subject to strange visions. Meanwhile, Marta recruits a team of miners to carry out a blasting operation in the abandoned tunnels beneath the city. The police suspect that the children's kidnapper is Luca, a Roma man who is Rafal's secret lover. Rafal disbelieves this and follows the money trail. He discovers that a German paid Ada to search for a mysterious Nazi treasure in one of the tunnels involved in Marta's blasting operation...

About to leave on an expedition to the Arctic, Lena Opalinska learns that Ada, her long-lost teenage daughter, and the kindergarten children she was looking after have disappeared. The geologist immediately goes to her hometown, where Ada lives, and enlists the help of Rafal, her childhood friend who has become an assistant commissioner. The police suspect Ada of kidnapping the children. Marta, a philanthropist and director of a sanatorium called Black Daisies where she experiments with the medical applications of anthracite, offers her support to the distressed parents...