Visus Mortuus

Why could Leah Derijker, a muggle, suddenly see the ghost of one Fred Weasley? 21-year-old Leah, a game developer in the muggle world met the ghost Fred Weasley, a fallen hero from a wizarding world, she never even knew about. Why was she the only one that could see him, talk to him. What is the link to this man she never met before. Her life is thrown upside down from the v