In the final weeks of World War II, a U.S. Navy warship exploded off the coast of New England, killing all but 13 survivors. Official reports concluded the tragedy was a mechanical failure, but questions arose about the possibility that a rogue German U-boat, hunting within sight of American shores, was the culprit. Now, 75 years later, an unlikely expedition team of citizen-detectives and professional divers have come together to scour the seafloor in hopes of finding the evidence that will finally solve the mystery of the USS Eagle 56.