Conan, Haibara, Agasa and the Detective Boys spend the weekend at a cottage with the three sisters who own it and the little sister's boyfriend. After dinner, the little sister realized she ran out of medicine and her boyfriend volunteers to walk through the storm to bring her more. Once the storm has ended, everyone decides to look for him since he was taking too long, and they find him dead on the snow.

Conan and the Detective Boys run into a man who had a knife in his hand and was being chased by a police officer. The man grabs Ayumi and faints while whispering something into her ear. Conan and the Detective Boys accompany the man and the police to the hospital and learn that he had some contusion on his head and the police officer was chasing him because he seemed suspicious.