Pneumonia, called Mr. Pneumonia, is sweeping through the Greenwich Village neighborhood where two women artists, Johnsy and Sue, live in a studio. A doctor comes and tells Sue that Johnsy will probably recover from the pneumonia if she believes she will. However, since she doesn't, he says her chance of dying is ninety percent.
Johnsy somehow believes that she will die when the last leaf falls from the vine outside her window. When the neighbor below, Mr. Behrman, also an artist, hears of this, he says he will paint his "masterpiece" and Johnsy will get well. Mr. Behrman has not had success as an artist, but the leaf he paints on the vine for Johnsy to look at outside her window is so detailed and realistic that she does think it is real. Because it never falls, she recovers.
Ironically, however, Mr. Behrman gets pneumonia by standing outside in bad weather painting the leaf that saves Johnsy. He dies—but he has painted his masterpiece, the last leaf.