Jiang Mu (played by Yu Shuxin) was a pampered younger sister before age nine, while Jin Chao (played by He Yu) was the favored elder brother. That year, their parents divorced, and their father and brother went to Thailand to make a living. At the age of 19, she learned the secret that her brother had been adopted and flew to Thailand alone without telling anyone. When they met again, the once elegant young man had turned from white to gray, a mechanic full of the sharpness of the common people, fighting in underground boxing rings and racing in black markets, facing numerous dangers in a world completely unfamiliar to her. From strangers to lovers, they ran towards each other between light and darkness. Adapted from the novel "Double Track" by Shi Jiuyuan.