Shinichi and Ran go to Tropical Land amusement park on a date. There they get involved in a murder case; it occurs when they are riding on the Mystery Coaster. In this case, there are seven suspects, including Gin and Vodka, the members of the Black Organization. Although Shinichi figures out who the murderer is and the trick, solving the case successfully…Later Shinichi follows Gin and Vodka because of their suspicious appearance, and therefore witnesses their illegal transaction. However, Gin sees Shinichi and attacks him from behind, forcing him to swallow their newly developed poison. Shinichi is consequently transformed into a child.The film recounts what happens elsewhere on the day Shinichi is turned into a child, his unspoken feelings for Ran the last time they are together, the real intentions of Gin and Vodka, etc. Adding new elements, it will be the true first episode not seen before!