One day, Grandpa Jeremi causes such a commotion at the retirement home that he’s threatened with transfer to a psychiatric hospital. Marta, his daughter, agrees to take him in, even though it’s difficult for her because Jeremi is unpredictable and has a vivid imagination. The situation is complicated by Marta’s daughter, Jagoda, who adores her grandfather and shares his wild ideas. When Jeremi refuses to live with his family, Jagoda decides to take matters into her own hands. The girl and her grandfather set off on an adventurous journey to the legendary ship Light of the Sea. They are pursued by Jagoda’s terrified mother and a gang of villains led by the wealthy Waldemar. And then there’s a dragon – it’s also after them.