It's early autumn and Dr. Headley eagerly demonstrates what seems to be a miraculous cure for tuberculosis. Not far from where he is working, the disease seems preparing to soon claim yet another life, a teenage girl named Winifred. Winifred's mother and little sister Trixie are devastated. When Trixie hears the family doctor say of Winifred that "when the last leaf falls, she will have passed away," she interprets the doctor's words literally. Thinking over what she has heard, she determines to do everything possible to save her sister.