C51 Accident or Murder?

"Sister, what are you talking about? Someone has tampered with the guardrail of Yue Yan's rooftop!" She widened her eyes in surprise and looked at Si Yan with a gloomy gaze. She said in a very subtle manner, "Isn't there surveillance cameras everywhere in the company? Moreover, Yue Yan's security has always been good. How can outsiders easily run to the top floor to destroy the fence? Sister