"The Defendant" revolves around a story about a powerful prosecutor who escapes from death row. The protagonist of the story is the best and most powerful prosecutor in the Republic of Korea who has never certified the guilt of the defendant. A series of unexpected events have reduced him to being locked up in a prison. What's worse is that he temporarily lost all his memories after a series of events, which has made it more difficult for him to clear his name. He also faced the worst dilemma in his life and began to fall into the desperate struggle of the prosecutor.