"Scars and Souvenirs," the 18th episode of Grey's Anatomy ’s third season, explores the emotional residue of the past through the arrival of Cristina Yang's former lover, Colin Marlowe, which threatens her relationship with Preston Burke. The episode contrasts painful "scars" with nostalgic "souvenirs" through various character arcs, including Alex Karev's connection with a patient and Meredith Grey’s strained relationship with her father.