Chen Jianguo, a deaf-mute repairman, is running a street stall in his residential community when he discovers that Xiaoyu, his six-year-old neighbor, is home alone and unconscious from gas poisoning. He desperately pounds on the door and calls for help, but his inability to speak leads to repeated misunderstandings and obstruction. Risking everything, he forces the door open and saves Xiaoyu, pulling her back from the brink of death. After Xiaoyu recovers, Old Chen quietly watches over her as she grows up, while revealing the painful story from ten years ago when he gave up on his granddaughter's rehabilitation, a decision he has regretted for the rest of his life. With the support of the community, he eventually launches a public welfare gas safety campaign called the Yaya Safety Guardians.