Modern supermarket owner Jiang Fan accidentally gets a magical censer that can connect to the ancient Da Qian Dynasty. When he learns that Yanmen Pass is besieged by Xiongnu and four hundred thousand soldiers and civilians are in a life-or-death desperate situation, he resolutely puts aside personal concerns, exhausts his family wealth to raise food and supply materials, crossing a millennium to send hope to the isolated city. Prince of Zhenbei Ling Luan leads the soldiers and civilians in bloody defense, fighting side by side with Jiang Fan through letters. Although separated by a millennium, the two write a cross-time-and-space national legend with kindness and responsibility, conveying the belief that ordinary people can also become heroes, and demonstrating the national spirit of mutual assistance and overcoming difficulties together.