The song "Hemmeligt Nummer" by Illusionisten is about a passionate and intense romance between two people. It describes the feeling of being completely absorbed in the moment, disregarding any consequences or judgments. The lyrics depict a sense of urgency and excitement, as the two characters engage in risky and daring behavior, fueled by their mutual attraction and desire for each other. The song also touches on themes of self-discovery and the idea of finding a sense of belonging and purpose in the presence of a loved one. Overall, the song captures the raw and intense emotions that come with being in a passionate and sometimes tumultuous relationship.