In this fanfiction, perhaps Harry Potter is brought into NCIS because there are rumors of a wizard - made weapon being used in crimes. He would have to navigate the non - magical world of law enforcement while also keeping his own magical identity a secret. His owl, Hedwig, could be used to send messages in a discreet way that NCIS could benefit from. He might also introduce some of his wizard friends, like Hermione, to help with research using magic - enhanced techniques.
One possible plot could be that Harry Potter uses his magical skills to solve a case that NCIS is stumped on. For example, he could use the spell 'Revelio' to find hidden evidence that normal forensic techniques couldn't detect. His knowledge of the wizarding world might also lead him to suspect that a suspect is using some form of dark magic or enchanted object in their crimes.
The plot could involve a magical artifact that Harry Potter is trying to protect. This artifact has somehow made its way into the world of NCIS. Dark wizards want to get their hands on it and will stop at nothing. Harry is in over his head as he tries to deal with both the Muggle law enforcement and the powerful magic of his enemies. NCIS agents, with their own code of honor and sense of justice, step in to rescue Harry. They start to learn about the magical world as they help him, and together they come up with a plan to keep the artifact safe and get Harry back to Hogwarts.
Maybe the Fem Harry Potter is being hunted by Voldemort's followers in a new and unexpected way. The NCIS agents rescue her, but then find out that there are spells on her that are affecting the Muggle world around them. They need to find a way to break the spells while also keeping her safe from the Death Eaters. This could lead to some interesting interactions between the two very different worlds.
In fanfiction, it could be that the NCIS has some sort of magical knowledge or artifacts. Maybe they've been dealing with cases that are on the fringes of the wizarding world without realizing it. When they discover that Harry Potter is in danger, they use this knowledge or these artifacts to save him. For instance, they could have an ancient amulet that can counter dark magic spells aimed at Harry.
Perhaps in this fanfiction, Harry Potter is recruited by the queen to solve some magical mysteries within the palace. He could use his knowledge of the wizarding world to uncover secrets that are plaguing the monarchy. For example, there might be a cursed object in the palace that is causing strange happenings, and Harry is the only one who can find and break the curse.
One idea could be that Harry is in need of a job after graduating from Hogwarts and ends up in Gordon Ramsay's kitchen. Harry's quick reflexes from his Quidditch days help him dodge flying pans and utensils when Gordon is in one of his angry chef moods. He also uses magic to keep the kitchen clean, which impresses Gordon, and they start creating magical - infused dishes together.
Well, it could be that the ICW has a special task force to deal with emerging magical threats. Harry, with his skills and reputation, is recruited. He might be sent to investigate strange magical occurrences that seem to be connected globally. He'd have to work with wizards from different cultures and magical traditions, which would be a big challenge but also an opportunity for him to grow as a wizard.
His magic could be used for forensic purposes. For instance, the 'Reparo' spell could fix broken evidence so it can be analyzed better. Also, the 'Accio' spell could be used to quickly retrieve evidence from a crime scene.
Another plot could involve a crossover of villains. A dark wizard from the Harry Potter universe teams up with a criminal that the NCIS has been chasing. Harry Potter and the NCIS agents then have to join forces to stop this unholy alliance. They would need to combine their skills, with the wizards using magic and the agents using their detective and combat skills.
The idea of a dark wizard being involved in a crime that NCIS is investigating is really engaging. It forces the two groups to collaborate. Also, the way some fanfictions handle the different forms of evidence is cool. In the Harry Potter world, evidence can be things like potion ingredients or spells, while in NCIS it's more about fingerprints and forensics. When these two types of evidence - gathering merge, it creates unique plot twists.