In June, 1944, U.S. Navy warplanes sank a Japanese submarine called the I-52 in the Atlantic, an event of enormous strategic importance. For the I-52 was to return to Japan with the lethal ingredients of a doomsday weapon-the radiological bomb-which remained a government secret for years. The "I-52"'s resting place became public in 1995. Author Richard N. Billings worked with Paul Tidwell-who discovered the I-52 and is attempting to salvage its precious gold cargo-in bringing this long-classified mission to light. Finally, this is the story of how the I-52 mission may have influenced President Truman's decision to bomb Hiroshima and Nagasaki.