Retired soldier king Tan Aotian wakes up severely injured, while Shen Bingqing suffers from amnesia and forgets their past. To protect her from the pursuit of the Underworld boss of the Blue Dragon Gang, Tan Aotian goes undercover as a security guard in the corporation. He successively resolves crises such as supply cuts by business rivals and lurking assassins, navigates various figures, and combats the side effects of the gene serum. In the ultimate rooftop battle, assassins turn sides to help, and the Underworld boss is subdued. Under the critical stimulus, Shen Bingqing recovers her memory, tears up her engagement, and stays with Tan Aotian.