Saboteur begins with a newlywed couple as they eat lunch waiting for their train back home to Harbin after their honeymoon in Muji. Mr. Chiu thinks about how grateful he is that his hepatitis didn't become worrisome over the honeymoon, he contracted acute hepatitis three months prior. As the couple eats, they hear police officers laughing at them, later one officer walks over to them and throws tea on their feet. Mr. Chiu demanded the police officer apologize to him and his wife. The officer refuses to admit the truth and arrests Mr. Chiu for sabotage. Mr. Chiu is taken to prison as he is taken out of the station he tells his wife to send somebody to get him out.
At the prison, he observes his room and notices it faces a spacious backyard. Later in the day, he is taken to the Interrogation Bureau and is met by the Chief of the Bureau. The Chief and the officer responsible for his arrest continue to refuse an apology. They show him the evidence stacked against him and demand Mr. Chiu confesses his crime. Mr. Chiu again demands an apology and is dragged out of the room. He eats dinner and began contracting a fever and worries about his liver, he notifies an officer on duty and is told he would have to wait until Monday.
Mr. Chiu wakes up that Sunday morning feeling refreshed and enjoyed sleeping alone after spending an abundance of time with his wife. He spent the day relaxing and waiting for someone to rescue him. He woke up on Monday to the sound of a man moaning out in pain. Mr. Chiu went to look out in the backyard and saw his old student, Fenjin, handcuffed to a tree. Mr. Chiu realized that his wife has stupidly sent this lawyer over to bail him out.
The guards took Mr. Chiu to speak with the Chief, again the Chief said he needed to sign his confession. Mr. Chiu protested until the chief said he would release both him and the lawyer in exchange for his signature. Mr. Chiu agreed and gathered Fenjin and left. As they walked back towards the train station Mr. Chiu told Fenjin how much he wanted to kill all of the officers and ate portions from every eatery up to the station spreading his hepatitis across Muji. Within a month eight hundred people became infected with hepatitis and six people died from the disease. No one knew how the epidemic started.
