Chapter 15 - "The Unbreakable Vow" - In which Hermione stays angry with Ron but Harry tries to stay friends with both, Harry finds that girls are trying to seduce him, and Romilda Vane tries to slip him a Love Potion. Harry then asks Luna to Slughorn's Christmas party, and Hermione invites McLaggen to upset Ron. After some general mingling at the party, Malfoy is caught prowling the corridors and Snape takes him away to an empty classroom, where Harry overhears Snape's offers to help Malfoy and Draco's refusals.
Ron Feels Inadequate
As Harry and Ron return from a lousy [Quidditch] practice, they run into Ginny and [Dean], kissing in a hidden passage. Ron yells at Ginny but Ginny embarasses him and walks off - leaving behind an angry Ron and a Harry who, for the first time, realizes he's attracted to her.
Harry and Ron walk back to Gryffindor Tower, Ron furious at Ginny and Harry confused over his feelings for her. Harry then all but admits he thinks Hermione snogged [Viktor Krum], and he and Ron both go up to bed, deep in thought.
Angry that Hermione snogged [Viktor Krum], Ron becomes moody and agressive, his [Quidditch] skills fall apart, and the night before the Gryffindor-Slytherin match, Harry tries unsuccessfully to spur his confidence.
Ron Feels Lucky
The Gryffindor-Slytherin Quidditch match. Draco Malfoy skips the match, [Zacharias Smith] commentates, and Gryffindor wins when Harry catches the Snitch right in front of [Harper], and Ginny celebrates by crashing into [Smith].
In the [locker room] following the [Quidditch] match, Hermione confronts Harry about slipping Ron [Felix Felicis] and Harry admits that he faked it - and both Ron and Hermione leave upset with each other.
"Hell Hath No Fury..."