So-jin, a DNA researcher, gets dumped by his boyfriend, Sang-min. Heartbroken, she drinks too much and breaks into a stranger's house. Yeon-woo, a successful gynaecologist, breaks up with his girlfriend as he gets sick of her. Kang-hoon, a hardworking firefighter, finds a pregnant woman unconscious. Meanwhile, So-jin witnesses Sang-min walking down the street with a woman she knows.