Mouri is invited to a party thrown by a famous singer, Suou. On the drive up, a tree branch blocks the road. There is an ominous note attached to the tree, warning them to stay away. When they arrive, they find the house is two wings connected only by a room on the second floor, where Suou keeps her creepy collection of masks, including cursed masks. Mouri is there to investigate one of the other party attendees, but also learns that Suou has been receiving threats about her charity foundation. That night Mouri relieves a phone call from the Phantom of the Cursed Masks, only to hear noises from the third floor - Suou's room. Locked from the inside, Mouri breaks the over frame glass and drops Conan into the room to unlock the door. Suou is dead in her room, the cursed masks scattered all around. The police arrive and verify there are no prints in the fresh snow, meaning someone from inside the house is the culprit. But how did they get into the locked room, and then how did they relock it?
