Lu Shen, a mathematical genius and newly promoted detective, solves crimes like solving equations, and his mouth is full of hot memes on the Internet. Jiangcheng City looks glamorous on the outside, but murders occur frequently behind the scenes. Bodies are hidden in sewers, buildings fall from rooftops, and the black market for plastic surgery is constant. His brain has a built-in "quantum crime-solving system". The more crimes he solves, the more accurate his modeling becomes, but a glass bottle numbered X-9 always flashes up. The clues point to Jiuweitang's miracle doctor Jiang Jiu - a cold-faced female doctor with a silver needle embroidered with "poison" on her waist. The secret of her missing ex-boyfriend is hidden in the medicine cabinet. The system key is actually her lover's brainwaves? Every unsolved case is getting closer to the truth: some people want to cleanse their memories, and some are willing to risk their heartbeats. Lu Shen complained about "this question about the underworld" and tightened Jiang Jiu's hand: "Come on, I will teach you how to solve the most difficult equation in life."
