Choi Bora (Jeon Do-yeon), who works at an English language institute, is having an affair with her ex-lover, Kim Il-beom (Joo Jin-mo).

Bora is disturbed when her lover appears to want to take the affair further and push past her boundaries, risking to expose their relationship.

Bora ends up drugging her own child, and Min-ki finds the toddler alone at home, and brings her to the hospital.

The movie then spirals towards its conclusion, with Min-ki apparently leaving by train, accompanied by his female friend, who lives in the same building.

Director Jung Ji-woo has taken the role of observer, using mostly handheld cameras to capture the events in the lives of his 3 main subjects.