Prince Zhi ultimately managed to return in time.
He withdrew fifty thousand troops from Yanmen Pass and joined forces with Enhui and others, bringing news back that His Majesty was safe, while Nian Gengyao was wounded and caused chaos.
This time, Nian Gengyao's defeat was like a collapsing mountain.
If The Empress Dowager were the one poisoned, and chaos ensued in the Capital, there would be time.
By then, starting a revolt in the Northwest and poisoning His Majesty in the Capital.
But... things didn't go as planned. The first one poisoned was His Majesty.
Moreover, the reaction in the Capital was so swift that Prince Zhi returned to the Northwest the very night.
Indeed, if The Empress Dowager died or fainted, it would merely be an affair within the imperial harem.
It wouldn't prompt such immediate vigilance. But His Majesty is different.
Thus, it's not surprising that Nian Gengyao lost now.
