Plot

A large real estate company held a social gathering aboard a cruise ship around Tokyo Bay. Then its president is fatally stabbed. The ship never once stopped and it is impossible for someone to board from the sea.

A large real estate company's social gathering is held on board the cruise ship 'Poseidon' as it goes around Tokyo Bay. Then the company president Kudo Ryoko (Nakano Yuta) is fatally stabbed. The ship never once stopped and it is impossible for someone to board from the sea. In other words, the murder scene is a "locked room aboard a ship". The suspects are three employees Takase Minami (Takimoto Miori), Mitsumine Yoko (Nakagoshi Noriko) and Narita Koki (Tonesaku Toshihide) who were together with Kudo. They unanimously complain of being "put to sleep by sleeping pill" and "waking up after the murder occurred". Detective Hagami Kyoko (Zaizen Naomi) of the First Investigative Division proceeds to investigate the case together with the young detective Kaburagi (Kiriyama Ren). However, a series of tragedies occur right in front of them. Mystery engenders mystery, darkness sucks in darkness. This is the "punishment" meted by Poseidon, the Greek god of the sea, to those who do wrong. Internal trouble, baffling human resources and gruesome cases that vanish in the vortex of time. Then the perfect crime of a lifetime. Will Kyoko be able to get to the criminal?—Okita Haruka, Nakayama Shichiri