One day Grandpa Jeremi causes such a commotion in the retirement home that he is threatened with transfer to a psychiatric hospital. Marta, his daughter, agrees to take him in, although this is difficult for her, since Jeremi is unpredictable and has a vivid imagination. The situation is complicated by Jagoda, Marta’s daughter, who adores her grandfather and shares his crazy ideas. When Jeremi refuses to live with the family, Jagoda decides to take matters into her own hands. The girl and grandfather embark on an adventurous journey to the legendary ship Light of the Sea.