The novel tells the mysterious and thrilling story of Tang Yi Xun and his beloved, Ye Hai Tang. When Hai Tang disappears without warning, Yi Xun finds a letter in his mailbox. He writes back and realizes that they are separated not only by distance, but also by time. Through twelve letters written over the course of thirty-five years, their bond endures as they seek truth and hope, weaving together love, longing, and the challenges of fate.