In a warehouse area at night, a drunk chief engineer is stabbed to death by someone who whistles. After the break of dawn, two seamen join the crew of a rusty cargo ship Kaiyo Maru. One is a troublemaker with bad attitudes, Senkichi Nomura, who pursues an enemy in order to take revenge for his father's death. The other is Keizo Sasaki, a buff, eagle-eyed man on board for a certain mission.