Fifteen-year-old Hou Xiao sets up a demon-catching stall at the Old Horse Market in Soto City, specializing in curing evil fire berserks, soul ring backlashes, and out-of-control martial souls. After Ma Hongjun visits, he accidentally stumbles into the underground soul demon fight, discovering that the soul arena is actually taking bets on soul masters turning into beasts, and someone is even using fake soul-stabilizing drugs to amplify desires and soul beasts' lingering obsessions. To save Qin Ya, Liu Shuang, and other soul masters forced into demons, Hou Xiao joins Shrek to track down the drug route, facing Lu Yan, the demon-raiser holding the Banner of Ten Thousand Beasts. One makes people win madly, while the other wants them to live soberly. When the demon-fighting bureau completely spins out of control, Hou Xiao finally understands that what needs to be caught has never been people, but out-of-control martial souls and the rules that drive people mad.