As Nathan (James Lafferty), Rachel (Danneel Harris) and Cooper's (guest star Michael Trucco) lives remain precarious following the car accident, Brooke (Sophia Bush) celebrates her 18th birthday but finds it diminished by her struggles with Peyton (Hilarie Burton). Lucas (Chad Michael Murray) and Karen (Moira Kelly) come to terms with her pregnancy and with the pregnancy of someone close to Lucas, while Deb's past addictions intersect with Haley (Bethany Joy Galeotti) in an explosive manner.