Kogoro, Ran, and Conan are invited to assist in a rooftop farm. Once there, they discover the elderly farmer, Takehiko Nakamura, dead from a head injury. The police are brought in and the other three farmers are interrogated for the death. Conan's discovers a shattered brick with a hole and discerning how Nakamura was murdered, tranquilizes Kogoro and reveals the farmer Marie Inoue to be the murderer. Conan reveals that she hung a brick on the handrail and concealed it with a towel and lured Nakamura to it with a phone call. When he was close enough, she pulled a rope connected to the brick hitting him on the forehead causing him to lose his balance and having him fall into the corner of the water tank. As evidence, Conan explains the towel's paint mark is from the handrail and that the rope must be in Inoue's home. Inoue confesses and reveals that Nakamura killed her crop which were grown from her father's final harvest.