The Goblet of Chaos by BlytheMondays — Chapters 39 to 48

Written by BlytheMondays. Fourth year goes sideways when Draco Malfoy saves Hermione Granger at the Quidditch World Cup, exposing a secret that could get them both killed. As the Triwizard Tournament returns with paired champions, disappearances, dark magic, and prophecy pull them into a dangerous alliance where loyalty and desire are almost as perilous as Voldemort's attention.