Joon Ki (Jang Hyuk) is a handsome former rugby player who has become a PE teacher. He works at a girls' high school, where he is immensely popular among the students. His wife Seo Yeon (Sun Woo Sun) is heavily pregnant with what will be their first child. Although he is happy with his family life, one of his pupils, Young Eun (Jo Bo Ah), falls for him and makes advances. Overcome with passion, Joon Ki succumbs to temptation and starts what he hopes will be no more than a brief fling with Young Eun. Once he comes to his senses, he tries to end the relationship and convince Young Eun to stay silent about what happened between the two of them. However, Young Eun’s love for him has now turned to obsession, and she refuses to end the relationship quietly. Things threaten to explode when one day he discovers that Young Eun has managed to convince his unsuspecting wife to tutor her…at their home. “Innocent Thing” is a 2014 thriller movie directed by Kim Tae Kyun.