On the day of his wife's birthday, Ye Xuan, who had lived in seclusion for many years, witnessed with his own eyes his beloved falling before him. The former king of mercenaries, Heilong, who once dominated the underworld and retired into the ordinary world to repay a debt of gratitude, works as an ordinary security guard at a real estate company, only wanting to live a peaceful life with his wife Qing'er. The case was hastily ruled as an accident, and the surveillance footage of the incident mysteriously vanished. Investigation pointed to the real estate company's young master and a mysterious mastermind. The king of mercenaries, dormant for ten years, returns to the underworld, vowing to ferret out all the true culprits and launch a thunderous revenge for his deceased wife.