Help with roleplay scenario

Hi all! I (26f) have never done roleplay in the bedroom. I got my boyfriend's consent to surprise him, and I have a plan I need help executing. Since our first date, "slutty detective" has been a recurring character in our relationship. It's just a joke, but i would like to make it into more than a joke. I bought a sexy detective's costume and a trench coat. He says he is OK with me showing up to his place with a trench coat and something sexy underneath (consent is key!!) I really want to take the role of "slutty detective" seriously and I need help building the scenario. Should sexy detective be questioning him? Should she be a corrupt/dirty detective? At some point, I for sure want to whip out a "I'm looking for hard, hard evidence." But I cant paint the scenario in my head. Anybody creative have any ideas?? Thank you all