Ran, Sonoko, and Conan run into their old third grade teacher, Akiko Yonehara, who invites them to spend the night at a Mountain Villa. A mysterious journalist arrives and tells them a massacre similar to three years before will happen that night. Can Conan help find the clues before too much damage occurs?
Attempted Murder
Location:Ski Lodge - 1F(Yonehara's room)
Victim:Akiko Yonehara
Suspects:Kohei Shimoda, Ryuichi Sakai, Minori Nakamura, and Atsushi Mori
While Sonoko was making bed, she heard a sound of Yonehara's glass fell on the floor in the next room and went there only to find Yonehara unconscious on the floor!
Suspects:Kohei Shimoda, Ryuichi Sakai, Minori Nakamura, and Atsushi Mori
As soon as Sonoko entered the room, the culprit appeared from behind the door and used anesthetic to put her to sleep then attempt to strangle her with rope!
Murder
Location:Ski Lodge - Front Door
Victim:Sugiyama
Cause of death:Strangulation
Suspects:Akiko Yonehara, Kohei Shimoda, Ryuichi Sakai, Minori Nakamura, and Atsushi Mori
When the doorbell rang, the group went to the front door only to find Sugiyama's body fall down in front of their eyes covered in snow!
Part 2
Conan is unable to figure out how a piece of rope disappeared, but when he figures out who is wearing a wig, he realizes that the person has killed two people on the same night. Using Ran to reveal the secret by using his own voice, Shinchi reveals the information to everyone present, but the revelation will shock everyone involved, especially Ran and Sonoko.
Both Nakamura and Yonehara heard a voice from cellphone from Shimoda's room and went to ask him to shut it off. They discovered that he was murdered! As Conan have been sitting at the stairway for entire night, one of the three teachers on the second floor must be the murderer who still has the weapon with his/herself, however after a body search, the weapon is not found!
With Agasa's help, Conan was able to get very important information about "Minako".
Suicide (Past)
Location:Haido Elementary School - Valleyball Club Room (Past)
Victim:Minako Mochizuki
Cause of death:Hanging
A girl named Minako was found hanged in Valleyball Club Room. It was speculated that the reason is she was stressed from an exam.
The killer was Akiko Yonehara, inspired by the death of little Minako Mochizuki. Minako had found out that Sugiyama and another teacher (Shimoda, but she didn't tell that to Yonehara) were involved in a fraud, and added that she was planning to confront the unnamed teacher. The little girl was found hanged in the school gym few days later, and Yonehara deduced that she had been killed by Sugiyama and his accomplice.
Knowing the identity of only one of Minako's two murderers, Yonehara organized the trip to gather the teachers that she knew Minako was a fan of. She first killed Sugiyama and left his body out there to freeze and trick people in regards to the time of his death; later, she attacked Sonoko to have an alibi, then immediately afterwards pretended to be a victim as well (using Sugiyama's body to such effects), and used her lipstick to spell out Minako's name in all of these cases. Shimoda's panicked reaction upon realizing the last detail revealed his involvment, so she tricked him into meeting up with her and killed him as well.
The murder weapon was her wig: she had cut her hair too short for her liking a while ago and hid it via long wig, and then decided to use it to strange her victims (excluding Sonoko as seen in the picture) without leaving clues.
The reason why Conan refrains from knocking out Ran is due to her nearly finding out his identity in The Cornered Famous Detective! Two Big Murder Cases. The anime omits this reason as it places the two stories in a different order.