Based on Henry Hervey's story ("Sky Over China," also known as "China Pass"), "Shanghai Express" was, in turn, loosely based on the May 6, 1923, incident in which a Shandong warlord captured the Shanghai to Beijing express train, where 25 westerners and 300 Chinese were taken hostage. All of the hostages captured in the Lincheng Outrage were successfully ransomed, including Lucy Aldrich. Paramount studio heads were concerned that the Hays Office kept a close watch on the film due to the portrayal of the Reverend Carmichael and the depiction of the Chinese revolution.