O. Henry was the pen name of William Sydney Porter (1862-1910), an American writer of outstanding short stories known for their wit, wordplay, warm characterization, and surprise endings.

'The Green Door' is a classic O. Henry tale. A young adventurer, strolling one evening along Broadway, is handed a card by a man advertising a dentist's services. But when he inspects the card, he discovers that the card given to him has on it only three words: 'The Green Door'.

Everyone around him has received a card for dental treatments. He returns and passes the tout again - and again receives a card saying 'The Green Door'. So the young man enters the next building in search of a green door....