Chen Yuanhang, a 28-year-old programmer, developed a smart wristband that helps elderly people prevent getting lost, but encountered numerous difficulties in its promotion. He accidentally met Lin Shufang, a retired teacher enthusiastic about public welfare, and the two joined hands with technology and warmth to build a safety defense line for the elderly in the community. When Grandpa Zhang, who suffers from Alzheimer's disease, got lost, the wristband sent out a key alarm, and a warm city-wide search was launched. This is a heartwarming story about technology for good and intergenerational mutual assistance.