In the story, a young salesman taking an evening stroll in New York City is handed a card which bears the mysterious handwritten words "The Green Door." Guided by the spirit of adventure, he finds a green door to an apartment in a dimly-lit hallway. His knock is answered by a girl living in extreme poverty. Before the evening is over, he comes to believe it was fate that brought them together.
"The Green Door" was adapted as a silent short film in 1917. Although it is not among the most famous, the story is often cited as a favorite by fans of O. Henry's works.
Rudolph Steiner is a young piano salesman living and working in New York City. He has a romantic soul and the rare, true spirit of adventure. On most evenings, he goes out in search of the unexpected and the egregious. His adventures do not always end pleasantly, but even misadventures are welcome to him.
One evening, Rudolph walks by a dentist's advertisement on the sidewalk. There is a tall black man in a flamboyant costume of red embroidered coat, yellow trousers, and a military cap in front of the building handing out business cards. Rudolph would usually ignore such advertisers, but the man somehow manages to slip a card into his hand.
Rudolph glances at the card and turns it over in surprise. It is a blank card with only three words handwritten on one side; "The Green Door." Rudolph sees a man throw down a card and picks it up. The card has the dentist's name, address, and the usual list of services printed on it. Intrigued, Rudolph crosses the street, walks back a block, re-crosses to the original side, and rejoins the stream of pedestrians to try again. For the second time, he is handed a card with only "The Green Door" written on it. He examines other discarded cards on the pavement and finds only the dentist's advertisements. He walks by the man for the third time, but this time receives only a cold look of disdain from him.
Stung by the look, Rudolph decides to dive into the adventure. He surveys the five-story building housing the dentist's practice. Above the stores and the dentist's, the top floors appear to be apartments. Walking up the stairs to the upper-floor tenements, Rudolph comes to a hallway dimly lit by two gas lights, one far to the right and one near him to the left. On the left side, he sees a green door. He knocks, and the door is opened by a young girl, not yet twenty and looking very pale. She sways weakly, and Rudolph catches her as she faints. He lays her down on a couch and looks around the room. It is obvious that the girl is extremely poor.
When she comes to and opens her eyes, Rudolph realizes right away that she is the one he has unknowingly been searching for in his adventures. He is shocked to find out that the girl has not eaten in three days. He dashes out and returns with as much food as he can carry. He helps her to a chair at the table and gives her milk, then some tea, then finally some food. At first, she simply eats like a starving animal. Then, as her strength returns, she begins to talk. Rudolph is very much affected by her story of low wages, lost time through illnesses, and lost positions.
Having eaten and feeling well, the girl suddenly becomes sleepy. Rudolph bids her goodnight but, in answer to her unspoken question, promises to come back the next day to check on her. Seeing him off, she asks how he came to knock at her door. Rudolph remembers the cards and, realizing they could have fallen into other hands, feels a pang of jealousy. He decides never to tell her that he knows about the strange means to which she was driven by desperation. Instead he tells her that he knocked on the wrong door.
After the door is closed, Rudolph goes along the hallway to explore the other end. He then goes up the stairs to the floor above. All the apartment doors are painted green. Going down to the sidewalk, he finds the tall man still handing out business cards. Rudolph asks the man why he gave him those cards, and the man points down the street at a theater. The sign above the door advertises a new play, The Green Door. The man explains that the theater agent gave him money to hand out some of their cards along with the dentist's.
Being a true follower of the twin spirits Romance and Adventure, Rudolph Steiner still believes it was the hand of Fate that helped him find the girl.