DOA Ethan Grohl is found on the Brooklyn Bridge with photos of a dead teenage girl named Mary in an envelope among his belongings. Sid locates a contact lens in Ethan's hair that Adam uses to find a DNA match to criminal Boyd Hackman. After talking to Mary's parents, Mac learns that they had a heated argument with their daughter before she ran away. The CSI's analyze the photos of Mary to discover tiny orange flakes on the print ridges and condensation on the face of her watch indicating she was alive at the time. Further examination of the photo reveals the Flatiron Building in the reflection of a broken bottle, which leads them to canvass apartments near the building, but to no avail. Flack studies Ethan's phone records and notes a multitude of calls to a young man named Oliver Epps. Jo ascertains that Oliver went to high school with Mary and that his calls to Ethan originated from the West Coast. Mac links the evidence to conclude that she ran away to be with Oliver and determines San Francisco as her destination given the fact that the orange flakes could only be found on the Golden Gate Bridge. Using the position of San Francisco's own Flatiron Building, the CSI's locate the apartment with the exact staging from the photos minus Mary. After Flack and Lovato track Boyd down in San Francisco, they get him to confess that he murdered Ethan and recover the stolen heroin bundle seen in prior surveillance footage. They identify the flower sticker on the bundle as a specific brand of high grade heroin distributed by a drug ring operating in the Haight-Ashbury district and head there to pursue Oliver. After a frenzied chase, Mac manages to take him down and interrogates him to learn that Mary is still alive. Oliver discloses that he helped Mary stage the photos to get back at her parents and directs them to the flophouse she has been staying at. They find her drugged out on heroin and take her back to New York to be reunited with her parents. Jo repairs the strain in her relationship with her daughter Ellie by being forthright about her former flame, FBI Agent Cade Conover, who also lends his help with the case.