|"Is this all real? Or has this been happening inside my head?"
The subject of this article is a real-life person, group, company, product, or creative work that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really exists), and, as such, details contained in this article may differ from real world facts.
The Flying Squad (or, in its Swedish translation, Kokain Nästet) was a novel, written by Edgar Wallace. Headmaster Albus Dumbledore kept a copy of its Swedish translation in his office at Hogwarts Castle, in the 1990s.