Earth God Bai Houtu manages the trivial matters of ten miles and eight towns, while Matchmaker Hong Sansheng ties marriages across the world. As the Qixi Festival approaches, Qinghe County suddenly experiences a city-wide wave of engagement cancellations; couples turn against each other, and the threads of fate are entangled with black threads. The two trace the clues to the old locust tree in the east of the city, discovering that the black threads grow back as soon as they are unraveled, and someone behind the scenes seems to be stirring up trouble using resentment. The clues point to an old affair from three hundred years ago, also untangling a forgotten romance. Can the red threads be retied, and who on earth is the person behind the black threads?