Je-In is a mystery novel writer. She chases after a serial killer with her longtime friend Rok-Hwan. Rok-Hwan is a detective. A handsome and mysterious man, Jason, appears in front of them.
Thud! Thud! Thud! The noise between rooms 401 and 501 has started! Eun Soo, an aspiring writer who is no different from a jobless person, begins to observe the owner of the house upstairs, questioning the noise between the floors that tormented her while searching for a subject for a contest. Ho Kyung, the man upstairs, also began to notice the existence of Eun Soo and eventually, Eun Soo faces a shocking truth... The noise that started today "Is the story that I only imagined real?’"
When raw gold is discovered deep in the woods, a group of gold hunters arrive to mine it. Several neighbors in the area witness the hunters by chance and find themselves in danger. Among the witnesses, hunter Ki-sung risks his life to protect the other witnesses and engages the gold hunters in a cat-and-mouse game of death.
A young women is raped while on her way home. When she is rejected by the police, because they don't believe her, she sets out revenge. But not only on her rapist, but also the police and everybody who did not believe her.
Yoo-ra suffers from nightmares every night. One day she meets her high school friends. Jin-tae is a promising artist, In-seok is a chaebol and former thug, Hye-jin likes In-seok, and Seong-ho, who used to be In-seok's errand boy, finally meet up. Yoo-ra asks her friends if they remember the classmate that killed herself. Everyone is flustered and claims they don't.
Yoo-ra goes to the bathroom, but passes out after seeing herself in the mirror. Everyone gets in In-seok's car to send Yoo-ra home, but they get into an accident and all become unconscious. When they wake up, they are at a familiar school that's closed. It was the school they went to that has closed down.
Jiwon, a motivated new police officer, is strangely bothered after meeting Osun, a social worker. On a hot summer day, a kidnapper sends a message saying, ‘If you want to save the kidnapped child, donate money to the welfare center.’ The incident becomes a national concern as the media report it. Somehow, Jiwon doubts the link between the case and Osun.
Trainee policeman, 'Sung-min' and job seeker, 'Jun-hyeok' were suspicious about a suicide incident of a girl who lived in the same dormitory, and they will be tracking her SNS account with the help of a private detective agency hacker, 'Nu-ri'. The investigation which started out of chivalry leads to uncontrollable consequences. These three people, Jun-hyeok, Sung-min, and Nu-ri become targets of SNS crime.
The three people, who have difficulty finding their common ground, open their eyes in an unknown space. Who, why, how where they locked up here? They can only escape if they find their lost memory!
20 year-old, Seol-hwa, is the most beautiful and pure. She works at a wine bar where men swarm just to see her. However, she is called the ice princess due to her emotionless expression which seems to hide a story. One day, to catch a glimpse of Seol-hwa, Jong-ho came to the bar, along with Do-jin who also fell for her. Seol-hwa is indifferent to Do-jin. Still, Do-jin invites Seol-hwa to his villa and somehow she immediately accepted. However, Seol-hwa appears in front of Do-jin with another man. Three people, and the purpose of their trips are different…