"This is my evidence."
Mr. Chiu unwittingly turns to metaphor to prove a case that by this point already seems for most readers to have taken on the figurative imagery associated with a Kafkaesque story. Mr. Chiu is being quite literal when he offers his damaged fingers as evidence with the immediately explanation that “Your man hurt my fingers with a pistol.” Long before Mr. Chiu recognizes that his situation has already slipped down into the murky netherworld of pure metaphor, his interrogator is already full in the thick of it. His response to the literal application of evidence to the damaged fingers is the same that anyone might well apply to a figurative legal argument: "That can't prove how your feet got wet. Besides, you could hurt your fingers by yourself."
“Egg of a tortoise!”
Almost certainly the strangest single line in the entire story for someone not familiar with Chinese culture is the mental insult that Mr. Chiu delivers to the police officer who quickly becomes his nemesis. “Egg of a tortoise” is an English translation that fails at almost every level in conveying the metaphorical put-down inscribed within the meaning of its original Chinese. One must be familiar with a mythic backstory of tortoises being thought capable of self-reproduction in order to understand that Mr. Chiu is with this strange image is calling into question in figurative terms the legitimacy of the policeman’s parentage.
“In his chest he felt as though there were a bomb."
This simile carries a hint of foreshadowing and a dash of irony. After all he’s been through with his arrested, interrogation and coerced confession on top of falling victim to a recurrence of hepatitis, Mr. Chiu could be forgiven for almost literally feeling like a bomb was ticking away inside his chest. The ironic foreshadowing is that, of course, he is already almost literal. He is on his way to becoming a kind of bomb that will unleash the genuine sickness inside as a pestilence upon the community.
Hepatitis
Mr. Chiu is afflicted with a serious case of viral hepatitis. Hepatitis of this type can essentially defined as an attack on the body’s immune system with the symptoms manifested as evidence of a body no longer capable of fighting off attacks to which it would naturally be so immune as to exhibit no symptoms being attacked. This literal illness can be read metaphorically in concert with Mr. Chiu’s seeming to apparently display a loss of immunity to more abstract concepts. Although it can hardly be argued that Mr. Chiu is at fault for his tragic experiences with the police, there is a case to be made that his overreaction contributes to deepening the tragic implications and thus can be interpreted metaphorically as a breakdown in his immunity to such overreaction.
Saboteur
As part of the metaphorically nightmarish world of Kafkaesque law enforcement in an authoritarian system the great irony of the story is that Mr. Chiu is processed within that very system from merely being a metaphorical saboteur into being a quite literal agent of sabotage.
