One Tree Hill: Season 4, Episode 16

4 - 16: You Call It Madness, But I Call It Love

It's Prom night, but things start to go awry as Lucas discovers who was the person in the hallway when Keith was killed, and psycho Derek holds Peyton hostage at her own house. Meanwhile, Haley and Nathan vow to be romantic with each other throughout the night, and Dan continues to win over Karen's affections.