Shadow's that Kill

AU - Canon Divergence - Hermione is a Lead investigator for the ministry. Scorpius gets murdered during a quidditch match by a dementor's kiss. Enlists Lupin for help. As both of them try to find out who the killer is, two more die. Who is controlling these dementors, and why? The main setting is a Quidditch pitch (posted first on archive of our own- 8/31/22)