The 9th annual Detective Conan movie sets sail on a 100 million yen luxurious cruise. Fifteen years ago, a cruise named Yashiromaru, built by the Yashiro group, sank while sailing. In the present, a new cruise, the Saint Aphrodite, was built by the Yashiro group and Conan and the rest were invited through Sonoko. Earlier, the husband of the CEO of the Yashiro family group, an established ship architect, had a heart-attack and drove his car down a cliff. On the second day of the cruise, the CEO herself was found murdered in her room. Later, her father, the President of the Yashiro group was also found missing. He had been thrown off the cruise into the ocean, seemingly by the same person. At the welcoming party, Kogoro shows off his deduction skills, and concluded that the sub-designer of the cruise, Akiyoshi, was the murderer. However, Conan has different ideas. Kusaka, a scriptwriter who worked in co-operation with Akiyoshi on a script, was the culprit. Kusaka reveals that the accident from 15 years ago was a scheme to sink the ship deliberately to get insurance. His father was murdered when he discovered the captain of the ship was drugged and left to die. Kusaka immediately set off bombs and escaped by sea and the Detective Boys gave chase. After they successfully took down the criminal, more bombs were ignited. All passengers were evacuated, but Ran returned to her hiding place during the hide-and-seek game to find a 'gold medal' made by sea-shells the Detective Boys made for her. However, as the ship swayed, she fainted in the enclosed area.