What really occurred on May 7, 1915, when a German U-boat torpedoed one of the largest luxury liners in the world, killing two-thirds of the 1,959 people aboard? Dr. Robert Ballard, the discoverer of the Titanic, investigates one of the most mysterious maritime tragedies in history. Martin Sheen narrates. 60 min. Standard; Soundtrack: English Dolby Digital stereo; "making of" documentary; bonus program "Last Voyage of the Andrea Doria."