Deaf Xiao Ma and his daughter Mumu rely on each other for companionship. The little "big sister" Mumu serves as the family's pillar—bridging communication between her father and the outside world, helping him secure work and earn a living. However, as Mumu grows older, she must integrate into the hearing world, and their inseparable life is about to be disrupted. Just then, a criminal syndicate that specifically preys on the deaf sets its sights on Xiao Ma. Desperate to protect his daughter, he is gradually lured step by step into the abyss of crime...