Si Jun specifically instructed the Prince Wei Mansion's carriage to take the main road, and deliberately rolled up the curtains so others could see him inside.
If Zhan Lan were to encounter any mishap or disappear, Si Jun planned to rush back to the mansion to establish evidence that he wasn't present.
He wanted to secretly torment Zhan Lan for a period of time, and when he ascended the throne, use Zhan Lan's life to threaten Mu Yan to crawl out of the Golden Throne Hall in disgrace!
After Hei Yu departed, he calculated the time—within an hour, Hei Yu should have brought Zhan Lan to his dungeon.
He intended to defile Zhan Lan's body, thoroughly torment her, and let Mu Yan live in a fate worse than death upon learning the truth!
But halfway through his journey, his asthma suddenly flared up.
His throat suddenly became dry and itchy, followed by coughing that grew more and more violent, as he began gasping for air.