High school student Sohee starts job training at a call center, but she faces pressure of greedy company. Detective Oh Yu-jin, who has something in common with Sohee starts to follow traces to reveal the truth.
One a bright spring day before a school trip, Semi, falls asleep on one side of the classroom, and suddenly awakens in tears over an ominous dream. She runs to Ha-eun, who is in the hospital after injuring her leg in a bicycle accident.
With high competitive spirit, a high school gangster Seung-in lets nobody to win over him. Hyun-tae is his best friend but wants to fight with nobody. One day, two boys get caught into a big fight that the local mobster is involved in, and they realize what true friends are.
An ace police crisis negotiator, Chae-yoon, is called to the scene where her supervisor is taken hostage. Through the control room monitor, she is faced with the cold-blooded hostage taker, Tae-gu, whose demeanors are difficult to interpret. Against the 21-hour deadline Tae-gu has set, Chae-yoon tirelessly tries to crack the unusually calm perp over multiple video-calls. Eventually, the shocking truth begins to unveil.
