Maggie Davis is a young girl who lives in Chester, Nova Scotia, near Halifax, when her beloved Uncle Nick is killed by diabetes. Maggie's father, a doctor, is greatly saddened by his brother's death, and soon has to deal with his own daughter's diagnosis with the dread disease. Various remedies are tried, including starvation diet popular at the time, but nothing works and Maggie's condition worsens. Meanwhile, in Toronto, Banting and other doctors work night and day to perfect insulin. Will they succeed in time to save Maggie and thousands of others?