Chapter 24: Sectumsempra

In Charms, Harry recounts retrieving Slughorn’s true memory and Dumbledore’s plan to hunt Horcruxes. Ron reveals he and Lavender split; Hermione adds Ginny and Dean have too. Katie Bell returns but still cannot recall who Imperiused her in the Three Broomsticks bathroom. Harry debates using Felix again and fixates on Ginny amid rising Quidditch stakes.

As the final match nears, practice excels with Katie back. Harry keeps failing to access the Room of Requirement and remains suspicious of Draco Malfoy. Spotting Malfoy with Moaning Myrtle in a boys’ bathroom, Harry overhears Malfoy’s fear of failing a deadly task. A duel erupts; cornered, Harry uses the unknown spell Sectumsempra, slashing Malfoy severely.

Snape storms in, heals Draco with a countercurse, and orders Harry to fetch all his books. Panicking, Harry hides the Half-Blood Prince’s Potions book in the Room of Requirement, marks the spot with a bust, wig, and tiara, and returns with Ron’s book instead. Snape exposes the ruse via “Roonil Wazlib” inside and assigns Harry Saturday detentions for the rest of term, making him miss the decisive match.

Back in the common room, news spreads. McGonagall confirms Harry is lucky to avoid expulsion and backs Snape’s punishment. Hermione condemns the Prince’s spell; Ginny defends Harry for stopping an apparent Unforgivable. Despite house anger, Harry reports for detention, performing mind-numbing file copying while the match is played.

Released after the game, Harry finds Gryffindor has won 450–140. Swept up in celebration, Harry kisses Ginny in front of everyone. Spotting Ron’s stunned look, Harry receives a small nod of acceptance. Harry and Ginny leave together, their relationship newly begun.