It's the ultimate "Who-Dunnit" when Roger Daltrey, the legendary lead singer of the rock group The Who, guest stars in a surprise role that will keep viewers guessing, on an upcoming episode of CSI: Crime Scene Investigation, Thursdays (9:00-10:00 PM, ET/PT) on CBS. The song "Who Are You," by The Who, has served as the theme song for the series since its inception in 2000.