Overview: The 11th season premiere of "History Detectives," which has been reformatted to focus on one iconic mystery per episode, opens with a look at the April 27, 1865, explosion of the Mississippi steamboat SS Sultana, which was packed with Union soldiers. One of the worst maritime disasters in U.S. history, the official death toll was 1547. The team reviews the original investigative report; and examines theories about the cause, including that it was an act of sabotage by a Confederate agent.