After his wife was killed, he began doubting everything

Someone brutally murders Young-hoon’s wife. A hair sample was found on his wife’s body and the detectives use it to trace it back to his friend Joon-sung and locks him up. Seemingly becoming a murder’s wife overnight, Da-yeon asks Young-hoon to testify on his behalf but when he doesn’t show up for the trial, she goes to visit him at his house.