講述了一個名叫李米的女的士司機和男友之間一段曲折離奇的愛情故事。某一天，李米的男友突然失蹤，李米失去了關於他的一切消息。之後李米開始收到一封封男友的來信，但是她每次找到寄信地址卻發現自己永遠都晚了一步。而在尋找的過程中，李米也發現，曾經深愛的男友其實是一個毒販。影片通過一些小人物的狀態反映了現代人生活上的壓力和精神上的迷失。愛一個人你會等多久？
Li Mi (played by Zhou Xun), a taxi driver, constantly mutters mysterious numbers and asks every passenger the same question: "Have you seen this man?" Her boyfriend, Fang Wen, has been missing for four years, yet he has continuously written letters during this time to keep her updated on his life. Unable to find him, Li Mi pastes his photo into a magazine, showing it to others in hopes of identification, all while living in a state of profound torment.
One day, she picks up two drug traffickers from Yunnan—Qiu Shuitian (Wang Baoqiang) and Qiu Huogui—who have come to Kunming for a deal. During the transaction, their "contact" inexplicably falls from a bridge to his death. In their panic, they encounter Li Mi, who has returned to give them their change; a desperate Qiu Huogui rushes into her taxi, intending to rob her to recoup his lost money and return home. Li Mi seizes a moment to call the police, but Qiu Shuitian ultimately lets her go after asking her to help find his first love, Xiaoxiang.
Meanwhile, the "contact" who fell from the bridge lands on the hood of a car driven by Ma Bing (Deng Chao) and Fei Fei (Wang Ning), resulting in his death; the couple finds themselves involuntarily entangled in the homicide case. Police officer Ye Qingcheng (Zhang Hanyu)—who is in the process of arresting the Qiu brothers—and Li Mi discover a startling lead: Ma Bing looks exactly like Fang Wen. However, Ma Bing remains indifferent to Li Mi's attempts at recognition. Is this the outcome Li Mi has waited four years for? Ye Qingcheng also begins to question Ma Bing's true identity.
