For nearly 45 years, the murder of 11-year-old Linda O'Keefe haunted the Newport Beach Police Department in California. Her image hung among the faces of other unsolved cases, reminding each new generation of officers of the work they still had to do. Could new technology and social media turn the tide? Correspondent Tracy Smith and 48 HOURS investigate the cold case and how an innovative Twitter campaign helped in the quest to find Linda O'Keefe's killer.