Residents of a mansion live in fear when a young girl is murdered. They suspect their neighbor for the crime, and a battle erupts to protect the next victim.

On a raining evening, middle-school student Yeo-Seon (Kim Sae-Ron), resident of a middle-class apartment complex, walks home alone from the bus stop, but she doesn't make it home. 10 days later, her decapitated body is found in a red suitcase. Gyung-Hee (Kim Yunjin) is Yeo-Seon's stepmother. She carries tremendous guilt, because she did not pick her up stepdaughter on the evening that she was abducted. A few days later, Gyung-Hee is so startled, she falls to the floor in the parking lot of her apartment complex. A girl stands in front of her. The young girl's name is Soo-Yeo (Kim Sae-Ron) and she carries an uncanny resemblance to her murdered stepdaughter. Soo-Yeo also lives in the same apartment complex. Another 10 days later, the murderer has yet to be caught and he has killed again. Meanwhile, several people in the apartment complex begin to suspect one of their own residents, Seung-Hyuk (Kim Sung-Kyun), is the serial killer, but they keep it to themselves for various reasons. The neighborhood pizza delivery boy (Do Ji-Han), the apartment complex security guard (Cheon Ho-Jin), the man who sold the red suitcase (Lim Ha-Ryong) and Gyung-Hee are all aware of circumstantial evidence that links Seung-Hyuk to the murders. Can and will they act upon their hunches before he strikes again?—asianwiki.com