I am working on a book for my kids (ages 10, 13) they love Harry Potter and similar books. I am writing a story about a private investigator that lives in a modern day but deals with various different fantasy elements like Orcs, vampires, witches, ECT. He eventually meets beautiful woman performing in opera that happens to be a Siren. The PI believes she is trouble but ends up having to save her. How do I get to the point of her being possible suspect then to being in need of saving? And hints of how the two falling in love in a teen/young reader story?