Passengers on a train are held by a Chinese revolutionary who takes a hostage to trade for his captured officer.
In Beijing Mrs. Haggerty (Louise Closser Hale) buys a train ticket to Shanghai. Shanghai Lily (Marlene Dietrich) arrives in a car dressed in black with a veil and hands her ticket to an officer. Henry Chang (Warner Oland) boards the train. Rev. Carmichael (Lawrence Grant) complains about Hui Fei (Anna May Wong), and he insists on getting another compartment. Captain Doc Harvey (Clive Brook) in uniform is talking from a window and is told that Shanghai Lily is aboard and that she is a notorious “coaster.” He asks what that is and is told such a woman lives by her wits along the China coast. Major Lenard (Emile Chautard) speaks in French. Mrs. Haggerty is worried about her dog being taken to another car.
The train starts moving, and Sam Salt (Eugene Pallette) offers to bet Chang that they will not arrive on time. Chang says Shanghai is in the middle of a civil war and that they will be lucky to arrive at all. Chinese get off the tracks, but a cow remains, stopping the train. Lily tells Doc she has not seen him for five years. She says he has not changed at all, and he admits she is more beautiful than ever. She says it took more than one man to change her name to Shanghai Lily. The track is clear, and the train moves slowly. Doc calls her Madeleine and says it was nice to see her again. Lily goes into a compartment with Hui Fei. Mrs. Haggerty asks to join them and comes in. She says she has a boarding house and hands out her cards. She only keeps respectable people. Hui Fei gives the card back and says she does not know her standard of respectability.
Rev. Carmichael tells Sam and Chang it is a shame they allow a woman of low moral character on the train. Sam says they are good-looking, and Shanghai Lily is in the next compartment. Carmichael goes out and in another compartment meets Dr. Donald Harvey. Carmichael warns him that the yellow and white women have rotten souls. Harvey wonders how he can see such things and says that Lily is a friend of his. Lily and Hui Fei go to dinner, and Lily asks Doc to accompany them. Sam says good evening and puts his hand on Hui Fei’s shoulder before going to the dining room. Lily asks Doc if the new ribbons on his coat are for bravery.
Chang asks Doc if he is coming, and they enter the dining room. The train stops where many soldiers are waiting. They are told to go out on the platform with their passports. They go out, and Carmichael complains. Outside Sam hides his jewelry and shows his passport. The officer checks each one. They search a tall Chinese man and arrest him. Doc wonders why, and Chang says he is probably a revolutionary trying to get back to his own line. They get back on the train, and it moves on.
Two telegrams are received on the train. Hui Fei asks Chang what he wants, and he says he is lonely. She removes his hands from her body. Sam asks Chang if he is Chinese or white. Chang says his mother was Chinese and his father white, but he is not proud of his white blood.
Lily asks Doc if he wants to be alone and joins him. She sees that he still has the watch she gave him with her picture in it. She has her arm around him and says they could see a lot of each other. He says he has an active life, and he does not want to be hurt again. She says she wanted to be certain that he loved her, and she lost and suffered for it. She pulls him toward her, and he kisses her. He wishes she had no other men. She says five years in China is a long time. He says they would have gone back to England and married. She returns his hat and says goodnight. She is given a letter and shows it to him. Carlisle wants to pick her up at the station in Shanghai. She throws away the letter.
The train stops. Chang goes in a building and speaks to soldiers. They go into action, and a machine gun starts shooting. Mrs. Haggerty locates her dog in a baggage car. A man says passengers are to get dressed and leave their luggage behind. They go into a building and hear more shooting. A soldier orders Mrs. Haggerty to follow him upstairs. Sam does not think they will get out alive. Doc says they are rebels and will not dare harm them. Sam wonders if Chang had something to do with it. Carmichael says he will not pay a ransom. Sam is called and implies they want his gems. Mrs. Haggerty says Chang is responsible. Hui Fei says there is a large reward for Chang. Eric Baum (Gustave von Seyffertitz) is called upstairs. Sam tells Mrs. Haggerty they got his phony gems.
Chang questions Baum and accuses him of dealing in opium. Baum says he deals in coal. Chang says the penalty for opium dealing is death. Baum is arrested, and Chang says it is for his insolence to him on the train.
Major Lenard is called, and an officer asks if anyone speaks French. Lily says she does and is told to go up with him. Chang asks him how long he was in the French army. Lenard says twenty years. He says he is visiting his sister and does not want her to know about his disgrace. Chang says he can go. Chang closes the door and is alone with Lily. He asks if she has any wealthy or influential friends. He asks why she is going to Shanghai, and she says she wants to buy a hat. He asks how she can afford to live in an expensive hotel. He asks her several questions and notes she is not married. He asks her to come with him. Captain Harvey is called, and Carmichael asks him to complain.
Chang questions Harvey and says an important officer of his was removed last night. Chang says he is looking for a hostage to trade for his officer. He asks why Harvey is going to Shanghai. Harvey says he is to perform an operation for a blood clot in the brain. Chang says he is important enough to get his officer back. Chang says he can only hold that village twelve hours. Harvey is locked in a room. The others are told to go back to the train and stay there.
At the British legation they learn that the Shanghai Express was held up and that they are holding Captain Harvey. Change gets a telegram that the Chinese government will trade the officer for Harvey. Chang shows the telegram to Lily and invites her for tea. He asks her to go with him to his palace. She says she has reformed. He offers to make it worth her while, and she tells him not to touch him. Harvey comes over and knocks Chang down. Chang says she is fortunate Harvey is her protector because he promised to return him alive.
Soldiers take Hui Fei upstairs as Lily comes down. Lily asks Carmichael to do something, and he suggests that she pray on her knees. She walks into the train and turns out the light in a compartment.
Soldiers wait as another train arrives. Two British officers get off, and the tall Chinese man returns to Chang. The British officer asks about Captain Harvey and goes up to get him. He comes back and tells Lily they would not let him go upstairs. Hui Fei goes into the train, and Lily follows her and stops her from using a knife on herself. Lily sees soldiers carrying a machine gun. She goes to Chang and asks him why he is holding Captain Harvey. She admits she loves him madly. Chang says she will have a chance to prove her love for him. Chang threatens to blind Harvey. Lily offers to pay them with jewels. Chang says it is not enough. Chang says all money could not wipe out his insult to him. She grabs a pistol, but soldiers restrain her. Chang says he admires her and says he could love her. She asks if his offer for her to go with him still holds; but he says he would not trust her. Lily gives her word of honor, and he believes it means something to her. Chang goes in and tells Harvey they are waiting for him. He burns the ropes, releasing Harvey, who says he would like to demonstrate his skill on him.
The British officer greets Captain Harvey and says they will leave in five minutes. All are aboard except Lily and the Chinese girl. The others get on the train. Lily’s luggage is being unloaded. Harvey goes and asks Chang why he is detaining her. Chang says he is not detaining her, and he asks Lily to tell him she is going with him freely. She says she decided to accept his offer. Harvey wishes them both a pleasant journey and walks away. Chang burns a paper. While he is looking at papers, Hui Fei stabs him in the back twice with her knife. She joins Harvey and tells him she killed Chang, and he had better get Lily out of there. Harvey goes in and gets Lily, knocking out two Chinese men. Harvey has a pistol, and he and Lily get on the train.
The train starts moving. Lily thanks Donald Harvey. She asks him where his watch is, and he says he probably lost it with some of his ideals. She offers to replace the watch but not the ideals. Lily goes into the compartment with Hui Fei and wonders if she should be grateful to her. Hui Fei says it is of no consequence. Hui Fei says she did not do it for her.
Lily listens to music on a phonograph. Doc Harvey treats Baum and says it will keep him for a while. He returns to others, and Sam asks how the invalid is. Mrs. Haggerty says Lily is the worst for wanting to go with Chang. Carmichael defends her, but Harvey disagrees because she said she was leaving with Chang of her own free will. Carmichael goes and demands to talk with Lily. He asks why she decided to leave with the barbarian who was killed. Lily asks why he wants to know. She says it is only her affair and might tell him if he won’t repeat it. She says he was going to take Captain Harvey’s eyesight. Carmichael says he will tell him despite his word. Lily says he will not. She says they loved each other and admits she still loves him. She doubts that he still loves her. Carmichael goes out and tells Harvey that he promised not to tell him. Carmichael says she is worth several people like him.
The train will be late in Shanghai. Lily leaves her compartment in her black dress. She goes to Harvey and asks for a cigarette. He gives her one and lights it for her. He says she is nervous because he touched her. He says that Carmichael told him that she prayed for him. He asks her why. She says she would have done it for anyone. She says goodnight and goes out.
The train arrives in Shanghai, and the passengers get off the train. Lily walks down the street alone and is about to buy a watch when Harvey sees her from the window. Hui Fei is interviewed by reporters. Sam says goodbye to Mrs. Haggerty and Dr. Harvey. Mr. Carmichael says goodbye to Lily, and she meets Major Lenard’s sister. Harvey tells British officers he must attend to something first. He asks Lily to forgive him for following her. She says she was buying him another watch. He asks her what good is a watch without her. She puts it on his wrist and says she wishes she could replace everything else too. She says goodbye. He says he won’t let her go out of his life again. He asks her to forgive him for his lack of faith. She says she loves him and always will. He asks how he can kiss her with so many people around. She says no one else is there. They embrace and kiss.
This drama portrays westerners in the midst of the Chinese revolution. A doctor without religious faith is contrasted to a minister who complains about low morals. Lily represents faith in romantic love, and the minister learns how worthy she is because of her love.