A murder mystery locked inside the world's first underwater train, racing between continents with nowhere to run. Ban Shunsaku boards with nothing but a killer's face and a dead client, forced to solve it before the voyage ends. The confined space turns every passenger into a suspect, the ocean itself becomes a pressure cooker, and a 1979 special about a 2002 future moves with the propulsive momentum of a train that cannot stop. The mystery escalates faster than the narrative can explain it. This is noir conducted in the deep, where the only way out is through.

The year is 2002, and the Marine Express, the first train to run under the sea between America and Japan, is about to make its maiden voyage. Its chief engineer fears the test run will be put to illicit use and hires private detective Ban Shunsaku. When Shunsaku reaches the man's mansion, he finds his client has just been murdered. Having caught only a brief look at the killer's face, he boards the Marine Express to uncover the truth, and the job turns out to be far bigger than he expected, because the train is hiding extraordinary secrets. The special mixes action, adventure, comedy, drama and science fiction.