The Big Bang Theory

Two girls go missing in a peaceful village a day after the SAT exam. While the evidence of murder is discovered but not the corpses, Jung-Woo, a model student and the classmate of the two missing girls, is suspected. She confesses but claims the blackout for not remembering anything. 10 years later, she serves out her sentence.

Jung-Woo arrives at a warehouse where the incident happened and falls in great agony over the memory of that day. Hearing about her mom's accident belatedly, Jung-Woo tries to determine the cause while everyone in the village distrusts her.

As Jung-Woo traces her mom's accident, detective Sang-Cheol suspects her when he finds out who Jung-Woo is. Ha-Seol, who got interested in the village's past incident, pays attention to the strange bone she found.

While the investigation of Boyoung's father, the key suspect in the fall of Jung-Woo's mom, is continued, Jung-Woo finally finds Boyoung and gets shocked.

Nakyum feels bad for Jung-Woo's circumstances and urges her to leave for Seoul together. An investigation of the past incident of Jung-Woo begins, and Sang-Cheol casts doubt on the case.

Boyoung's mom's demand provokes Goo-Tak. Also, Ha-Seol notices something strange from the village neighbors when Su-Oh falls into a fit. Meanwhile, Ha-Seol is astonished to see Su-Oh back from the hospital, who seems completely different.

The one who threatened Jung-Woo with a gun was Boyoung's father, who got released. Gun-Oh suddenly comes back from the States, and the way Goo-Tak looks at Gun-Oh is suspicious.

Jung-Woo gets shattered by the thing inside Gun-Oh's bag he brought. Su-Oh, trapped in the mental hospital, tries to tell Ha-Seol the secrets.

Sang-Cheol strikes against Byeong-Moo, who tries to block Gun-Oh's investigation. Simultaneously, Minsu discloses the truth.

Goo-Tak gets devasted by Gun-Oh's suicide. Na-Kyum reveals to Boyoung's parents that Byeong-Mu and Minsu are involved in Boyoung's death, and the entire village becomes enraged.

When Byeong-Moo gets arrested, Byeong Moo's father blames Min-su for it, and a fight breaks out between the fathers. Na-Kyum confesses to Jung-Woo that Byeong-Moo has been threatening him all this time.

The warehouse opens, and the truth comes out. Hyeong-Sik, the head of the hospital, tells his wife that he is being threatened when his wife comes across the ring, and the fight between Boyoung's parents intensifies.

Shocking truths continuously come out since the shooting of Boyoung's father. Hyeong-Sik panics, and Sang-Cheol presses Goo-Tak.

Jung-Woo feels despondent over the death of Minsu's father, who couldn't disclose the crime. Simultaneously, the funeral of Boyoung is held, and Sang-Cheol accelerates the investigation.

Na-Kyum reveals the astonishing truth of that night. Jung-Woo, who knows every matter at last, faces a dangerous situation.

Jung-Woo desperately hopes her mom can recover. The gubernatorial election rises to a peak, and the door to one last truth opens.