Ten years ago, immediately after a young Kudo Shinichi meets Akai Shuichi's family on the beach, a car falls off a cliff. It becomes clear the car belonged to two thieves who robbed a watchmaker. The driver died immediately, but their accomplice fled from the sinking car and blended in with the crowd on the beach. With the help of Shinichi and his friends, Shuichi narrows down the suspects to Fukumizu Shigekatsu, Kitamori Yasue, and Oami Raiya. The police detective decides to question the three of them, and Shuichi determines which of them is the robber based on their testimony...