Manabu Yukawa has traveled to Hari Cove, a once-popular summer resort town fallen on hard times. He's there to speak at a conference on a planned underwater mining operation. The night after the tense panel discussion, one of the resort's guests is found dead at the base of the local cliffs. The police believe it was a simple accident. But when they discover that the victim was a former policeman and that the cause of death was carbon monoxide poisoning, they suspect he was murdered, and his body tossed off the cliff to misdirect the police. As the police try to uncover where Tsukahara was killed and why, Yukawa finds himself in another mystery.