Until its recovery in 1995, the sunken Civil War submarine H.L. Hunley has rested undisturbed at the bottom of the Atlantic Ocean. As experts explore the wreck and remove layers of corroded material, answers to long-hidden secrets about why it never returned from its 1864 Confederate mission begin to emerge. Using new evidence and 3D modeling, this special reconstructs the Hunley and solves the mystery surrounding its disastrous demise.